Is your stitched macOS PDF unreadable by Adobe Acrobat? “Export to PDF” solves this.

A PDF I sent students was unreadable by a friend trying to read the file on Adobe Acrobat Reader n a desktop PC. This felt like a repeat of a problem I experienced in 2019 with macOS Catalina. And I had thought a Catalina update had fixed the error.

This time, on the Big Sur 11.3 Beta, the problem surfaced after I had stitched two PDF files in macOS Preview. The resulting PDF was not completely readable by Acrobat on either a PC or Mac. Page 5 of the 7 page document produced this error message:


A solution had been suggested for this new problem on this Adobe forum last year for macOS Mojave – when viewing the combined file in Preview, choose File > “Export as PDF” to generate a “true” PDF file. I tried this and indeed Acrobat could read all the pages. 

Looks like it accurate to say macOS Preview corrupts a stitched PDF – goodness! Good to know.

Video freeze whilst screen sharing in Zoom, on macOS Big Sur? Reinstall Zoom and enable “Use TCP connection for screen sharing”

Update – this note explains this will be resolved with the next Zoom for Mac update (after Ver 5.5.4). Thanks Kenneth Pinto!

My animal behaviour videos froze during the past two lectures. The problem first happened mid-lecture in mid-February which sure had me scrambling, as the short videos are integral to the lesson. This morning the freezing more polite surfaced during the pre-lecture video. I plan a short, relevant video as an AV check with students, and they reported the frozen video.

On both occasions, I was on my wired iMac with BigSur 11.2.2 and I switched to my wireless laptop on macOS Big Sur 11.3 beta and continued the lesson without a hitch [update: the problem was with wired macs]. A search revealed the solution: macOS Reddit user @portzebie was told by Zoom Support to i) uninstall and reinstall the Zoom desktop client, and then ii) go to Zoom preferences > Share Screen > Advanced options > enable “Use TCP connection for screen sharing”. Oh, and iii) restart your Mac!

Zoom  Enable TCP in Screen Sharing

This seems to have worked. Restart your Mac if all is not well at first.

I think tere are some other hiccups with Keynote (“Play” versus “Play in Window”) and with Zoom Screen sharing (enable “Optimise for Video Clip” or not) still. I shall sort that out before my next lecture.

But let me me restart that iMac first.

Zoom Optimise for Video Clip

Singapore residents have free access to the print version of The Straits Times (Singpass or NLB account)

If you need to read a premium article in the local papers (I.e. paywall), and are a Singapore residents (with SingPass or an NLB account), you can access The Straits Times, The Business and six other SPH publications for free.

The free access was introduced in late April this year during “Circuit Breaker”, the mitigation response to the COVId-19 pandemic. This service was been extended indefinitely.

Just visit this NLB page You can increase the text magnification to a comfortable size.

ST 2 page view

On a related note, NUS staff and students have access to newspaper and media archives in Factiva and Nexis Uni; just look up

Using your iMac camera? A 3rd party 1080p webcam shines a light on your conferencing

I brought my iMac (late 2015) back from work when my MacBok Pro was sent to the shop. Immediately it was clear the iMac camera quality was inferior. Apparently Mac users have been frothing at the mouth for years and that escalated when we all went online and WFH for COVID-19 – especially if your workspace at home is not well lit.

So much so the improved camera on the 2020 iMac is cause for celebration!

If I had to shop for a camera, the options online would have defeated me. Thankfully the department just issued staff with a GSou 1080p T16s webcam which they purchased from the co-op. A quick look online has it on sale for $34. And there are cheaper 1080p cameras for less than $20, if you would care to experiment.

So I added the GSou webcam clumsily on top of the iMac this morning and here is the difference:

iMac (late 2015) 720p (UVC Camera VendorID_1452 ProductID_34065)
GSou 1080p T16s webcam

Although it will break the sleek online of your iMac, add a 3rd party 1080p webcam to improve your appearance during meetings – it will help everyone on your conference too.

Unless you are Deep Throat, and need to embrace the dark.

Are you backed-up and protected? Predators are prowling amidst the COVID-19 WFH prey!

In the 80’s and 90’s, many a thesis writer lost their minds after a hard disk crash. Tears would flow freely and those were tough times. On one instance, someone thumped the door of the Ecolab at the Department of Zoology. It was middle of the night but door thumper Adrian Elangovan knew we’d be awake and set me on the problem. It was a PC of a PhD student in a very warm room full of humming equipment, while under-powered air-conditioners creaked in defiance of the though of providing cool air.

Thankfully, it was merely a Windows OS crash, so some commands for the underlying DOS system saved the day! I left him with an F2 key which would back up his wordprocessor files to an external 135MB disk.

No more adventured these days, thankfully, because of cloud storage. This is why all my research students get a Dropbox Pro account once they begin.

Research student folder
Research student’s project Dropbox folder, all synced with me

A new problem has emerged for the times ad its ransomware! An honours student was ransomed but didn’t cough up the required bitcoins. Instead she alerted me to stop sync-ing at my end and to stop my occasional local backup. Her warning delivered, she for Dropbox’s help to recover the most recent healthy version of the file and all was well.

My current cloud and local back up protocol has been in place at least since 2015 which has allowed me to shrug off the sudden death of several overworked laptops and easily update my most recent 15.1″ Mac Book Pro.

Well, fast forward a few years later and it seems we are still a juicy target in Singapore; just two weeks ago, “Microsoft has warned that Singapore has suffered from more drive-by download attacks [malware insertions] than any other country in the Asia Pacific region in 2019.

While there was a 27% decline in region, “…Singapore experienced a 138.5 per cent rise.” [“Microsoft warns of spike in drive-by download attacks in Singapore,” by Hariz Baharudin, 17 Jun 2020 (link)]

Keir Thomas at MacWorld write recently to remind us of the good news: all this while, macOS has anti-malware protection built in. Go to Apple > About this Mac > System Report > Software > Installations > XProtect – I checked and it had just been updated (30 Jun 2020). Just as well, since ere are always new variants afoot.

macOS antimalware
macOS has anti-malware called XProtect, which gets updated

Now, with lots of us working from home during COVID-19, many of us will fall short of enterprise-level protection and this has surely meant more mischief must be afoot. While government and corporates fight off daily attacks, we need protection too. And not all feel macOS’ XProtect will suffice.

I have been using Sophos’ free antivirus and there is no performance bump on my 32GB RAM Macs. Get this free software if nothing else. And if you feel jittery, the paid plans add further protections including ransomware, and come well recommended by MacWorld.

Sophos Plans
Basics are free, more protection with payment

Mind you, Tom’s Guide and TechRadar Pro and PCMag all say BitDefender, which you can get for an even cheaper price right now.

Do we macOS users need any of it? Attacks are not unheard of, but not common, so it all depends on your appetite for risk, doesn’t it? But before you check out software, do attend to some basic settings first. Peace of mind is priceless!

Click Meeter for your next online video meeting and organise your windows with Magnet [macOS]

Here are two really helpful apps which help me in my work online.

Meeter picks out video conferencing meetings scheduled in my Exchange and Google calendars, and lists them in the menubar – which I call up with a keystroke, typically 15 or 30 mins early for meetings I host.

Meeter menubar

I’ve set Meeter to present meetings links five mins early in case I forget to join a meeting I signed up for. With just a click, I’ve joined the meeting. That is typically on Zoom, but Meeter works for Webex, MS Teams and Google Meet as well, amongst others.


The second app has been critical during webinars – I typically have several widows open which I refer to, in addition to the video conferencing app. The Q&A window is on a separate separately, I look up references the speakers make on a web browser, I may be chatting with audience members on What’s App, and keep Notes open to take notes.

Magnet organises all my windows, again with keystrokes. I push windows around with keystrokes to various positions – left or right or top right or left two-thirds. It has been critical when I was using just my laptop screen, and is still very useful when use two screens during WFH.


Go get ‘em!

Educators can use Zoom safely – just explore the settings

Since the onset of COVID-19 in late January, I’ve been video-conferencing meetings. My go to for years have been Google Hangouts and Skype with students, and since last October, Microsoft Teams with staff. The latter was part of an effort to shift college colleagues from a bunch of unsecured Google tools to the more secure though less friendly Microsoft platform.  

One I started using Zoom though, these other tools were forgotten. Zoom was a delight to use, with an easy interface and single click invitations to a web interface for novice participants. For educators managing classes, the Waiting Room and Breakout Rooms were extremely useful.

So in the final instructional week of the shortened semester (Week 12), I scheduled some 400 students in two modules to present their final oral presentations. That worked out to more than 80 half-hour sessions with Zoom over four days, of which I attended almost 50.  

Since I was imposing a tool on so many of us, I read up, prepared guidelines (posted on Google Docs), and compiled this list below to train staff and myself about our hosting duties:

Zoom for Educators: Security responsibilities for hosts
Edit your settings at: 

  1. Use the latest version of the Zoom app (check for updates)
  2. Generate a new Meeting ID for each meeting
  3. Generate a new secure password for the meeting
  4. Nominate a co-host when scheduling the session
  5. Keep the Meeting ID and password private to participants only. For large meetings, I have people sign up first and email them meeting details.
  6. Advice participants they can set a Virtual Desktop to mask their background.
  7. Disable File Sharing
  8. Use the Waiting Room to vet participants before allowing them into a session (participants must have recognisable usernames)
  9. Disable “join before host” but be 15 minutes early to the meeting in case participants need help.
  10. Enable the authenticated user mode, if possible.
  11. Lock the room when all are present and if connections are stable.
  12. Set the screen sharing default to host only; release as needed
  13. Respect your participants – inform them if you are saving session chats or video-recording the session.

Since students were new to this, I didn’t enable the authenticated user mode nor lock the room for ease of those with dropped connections.

So the homework was important.  

Zoom’s Virtual Desktop was a fun tool with which to encourage others to use the app.

The National University of Singapore had initiated COVID-19 mitigation measures by Chinese New Year. And almost immediately, the Centre for Instructional Technology rolled out e-learning solutions. Amongst others, they promoted the use of Zoom, complete with training webinars. The staff I worked with attended these sessions, were familiarised with fundamentals for use and explored the pedagogical outlook.

I was still using Google Hangouts in March 2020 with research students and Teams with staff. However by late February (Recess Week), the shift to 100% e-learning appeared inevitable, which meant our student symposia in April would have to be held online. I had about 300 students in GEQ1917 Understanding and Critiquing Sustainability at RVRC and another 100+ in LSM1303 Animal Behaviour at Department of Biological Sciences. 

So I began reading about Zoom and the problems were highlighted by many tech sites. Some critical issues had been fixed the previous year, and several others could be circumvented by choices in the settings (hence the list above). While some didn’t matter, such as end to end encryption for what would otherwise be public symposia.

All that scrutiny was helpful, as it eventually forced Zoom to announce a focus of their engineering effort on privacy and security. Already a security

Many articles hysterically bemoaned the shortcomings, and while useful to carefully sift through for weaknesses, no alternatives were suggested. As with every tool, it would eventually be the examination of the purpose and settings that would decide if safe use was possible for my purpose.

I was glad to see that NUS’ CIT announce this position calmly twice, as did Tech Editor Irene Tham in The Straits Times. 

It was understandable that the Ministry of Education had to swoop in to ban the use of Zoom after a hacking incident, which made world news. But that ban is temporary, for as reported in The Straits Times “the ministry is working with Zoom to enhance its security and make security measures clear and easy to follow.” [Update: they have restored Zoom with some limits in place and will review in future – link]

Since practise with settings and short cuts is critical, I suggest you try this with friends, and incite the tech savvy ones help with an online tutorial. After preparing a friend for her seminar, I learnt a few more things myself.

Since January, a variety of COVID-19 mitigations have been in place in Singapore, and we now all have plenty of friends to experiment tele-conferencing tools with. I’ve had fun scheduling sessions in a jiffy with my secondary school buddies and it has also been a great way to support each other during this challenging time.

Useful links:

Fortinet Client v6.2 for macOS for use with NUS SoC VPN

I started using the Forticlient for macOS when I was in China for the International Otter Congress. One of my Chinese students from SoC introduced me to the alternative to NUS VPN which use Pulse Secure. I had been having problems after macOS Catalina came out so I switched to Forticlient which worked.

Once installed, I just have to set the remote gateway to and I’m good to go. It’s not in App Store so is not automatically updated. I was installing it on a temporary machine while my MBP was in the shop (for a keyboard change) and realised the client is now at version 6.2. Updated!

Screenshot 1363

PDFs generated by Keynote unreadable by Adobe Acrobat (macOS Catalina, 10.15) – use a browser!

Update – if you stitch PDFs with macOS’ Preview, the Adobe Acrobat for Mac (and PC) will be unable to read the entire file. Even on Big Sur Beta 11.3 Beta 5. Solution: “export to PDF” from within Preview.

I dived into macOS Catalina since I had few 32-bit applications. Also I was feeling reckless and did not wait for the end of semester like I typically would. Thankfully, most of my apps were updated to 64-bit and I could afford to abandon the few legacy apps.

There was just a problem with PDFs. I print my Keynote lecture slide deck to PDF for distribution to students. NXPowerLite Desktop 8 reduces the file size by 90% for a manageable download of 10-20 MB. 

But after macOS Catalina installation, my student Ivy Yeo, who uses Adobe Acrobat on a PC, alerted me that she could not open my PDF. I duplicated the problem on macOS Adobe Acrobat which also returned a blank page and the error message, “There was a problem reading this document (14).”

WhatsApp Image 2019 10 15 at 10 15 09 PM
Uh-oh! Unreadable lecture notes!

A few minutes later, though, she suggested using browser to open the PDF – she used Chrome on a PC while I used Safari. The printed PDF could now be read by Adobe Acrobat. 

WhatsApp Image 2019 10 15 at 10 42 56 PM
Phew! Ivy’s solution – use a browser to read and print the PDF

After consulting forums and webpages, I suspect that Keynote on macOS Catalina is now adding metadata which Acrobat is choking on. The simple pdf readers inbuilt in browsers dump that additional data and could read the stripped file. 

The workaround is excellent, but adds a couple of steps each time. So I hope one of the macOS Catalina updates fixes this soon!