For my problem-solving classes I prepare presentations which include a reminder on the theoretical parts, statements of the problems to be solved, some (partial) solutions, tips and so on. These presentations are then displayed to the students by means of the screen sharing. Then we discuss the problems, try various approaches and do the usual stuff one would do in an offline class with a black- or whiteboard.

We mostly use Zoom which includes commenting tools which we actively use in the process. The comments and the drawings stay where they are when I go over the pages of the PDF, so when we switch to another slide, I have to clear the comments. It is mostly okay, but there are two issues:

  • When one of the students asks to get back to one of the previous slides, all the comments are gone (this is even more relevant for the research seminars).
  • The comments are not saved, meaning that the presentation I would share after the class contains no comments we made during the session (in particular, the solutions to the problems we solved in class). We record the video, sure, but the students told me that the slides themselves are more convenient for later use.

Now Adobe Reader and other PDF reading programs also contain the commenting and drawing tools, and all the comments can be saved in the document, but the comments are attached to the pages of the PDF and not to the slides, so I cannot combine drawing on top of the slide while also turning the pages of a single slide (in order to reveal something I prepared in advance).

Q: Is there a way to combine these features, so that the comments are not lost, while also not tied to specific pages, but rather to the blocks of pages (say, for the sections of the PDF)?

  • Take a screenshot before changing slides.
    – Solar Mike
    Apr 19, 2020 at 10:21
  • Not a short term solution, but you might suggest a feature request to Zoom or others.
    – Buffy
    Apr 19, 2020 at 13:03

2 Answers 2


If you use webex at least one part of your problem is solved. In Webex the comments I do stay with the slides.

Zoom is somewhat funny regarding the defaults: A scribble on one page of a presentation is rarely relevant to the next page. But that's zooms default behaviour. And yes it's rather annoying to erase each time you change slides.


A possibility (the one I use, actually) is to load the PDF presentation into a whiteboard software, and then share the screen.

For instance, I use OpenBoard as whiteboard software, but I suggest you to explore other software as well (I find OpenBoard a bit clunky at times).

The whiteboard software typically also allows you to save the annotated PDF, so that you can share the annotated slides with your students. Below an example of annotated slide. One drawback, at least with OpenBoard, is that the PDF is transformed into a bitmap image, loosing a bit of resolution.

enter image description here

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .