Sumatra PDF is a PDF, ePub, MOBI, CHM, XPS, DjVu, CBZ, CBR reader for Windows

[Fixed] Highlighting problem in prerelease version

I use prerelease 3.2.11495 version.
How can I highlight text?
I tried seletcing text then press A, H, both didn’t work. Did I miss something?
I browse a lots of topic relating to this but all the answers are about “You need to use prerelease verion and advice about setting savedocument to false, etc.”.
I can’t find anyone with same problem as me.

Thank you!

The highlight key is A for annotation and ONLY available in pre-release builds it generally works in many formats such as TXT AZW & MOBi etc.
HOWEVER there is a current problem (since the major MuPDF update including 11495) with it writing in PDF, although highlights from older pre-releases are still shown both from SMX files and those appended by MuPDF to the PDF.

Oh Thank you for the information!
Is there anywhere I can download the prerelease version < 11495 ?
If that’s impossible, what would you recommned as a temporary alternative ? because I really love highlighting!

Thank you in advance :slight_smile:

I cannot recommend downloading any “foreign” historic copies and many updated clones also will also not provide the function.

However the good news is there is something better :slight_smile: in using the MuPDF-GL annotation feature which includes add text / comments etc. It can be a bit odd to work with and WILL change the PDF content when you save the PDF,
The latest download is 78MB from and you only need the one mupdf-gl.exe from it which is a “lightweight” 34.7MB but it avoids using pre-release if you only want to annotate PDF as it works perfectly with the formal release (currently 3.1.2)

It is not the easiest to use but should be 100% compatible with SumatraPDF reading the annotated files.

Open a COPY of a PDF and press “A” then have fun testing what you can do but beware large objects can overlay small objects which then makes it difficult to change them later.

If you want to add an external viewer command to call the pdf page you need something like

ExternalViewers [
		CommandLine = "C:\     wherever I keep it    \mupdf-gl.exe" "%1" %p
		Name = MuPDF-GL PDF annotator
		Filter = *.pdf

When a PDF is open you get an extra FILE command to
Open in MuPDF-GL PDF annotator

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I have my SumatraPDF set to update all the time and I apply them… why does it seem I’ve lost the ability to highlight?

Any help would be greatly appreciated

@mva1985 welcome

Highlighting in PDF and XPS is temporarily not visible in pre-release (it is working but invisible)
If you save as it will save your highlights :slight_smile: which you can then read using the formal release

The alternative way of using MuPDF-GL to make permanant changes to a PDF (not xps or other formats like .txt) is described above.

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I’m not trying to be thick, but can I add highlights in the prerelease versions?

Cause when I select some text and press ‘A’ it doesn’t appear to be highlighted. Is this what you mean by invisible?

Thanks for your fast response to my initial question

It’s temporarily disabled due to changes done in rewrite. I’ll enable it at some point.


Thank you so much @GitHubRulesOK!
Sorry for late response. It was near the exam time. I chose to stay at university and studied at a library using ipad instead of going back home then I forgot that I created this thread until new notifications reminded me T_T
I will definitely try out mupdf method mentioned when I read pdf on pc again while also waiting for new pre-release version with highlight fixed :slight_smile:

Thank you!

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hi all, here to say great work on Sumatra pdf , love it!!
posting here because i just tried downloading the prerelease to test the highlight function (which would be a BIG plus for me), but it’s not working for me! anyone else have this problem? When i press “a” after highlighting 1 or more words a small icon appears briefly in the upper right of the screen to signify something is broken i think.
ps ever considered moving to Gitlab, it’s open source, Github isn’t !

The highlight is added when you press A that is the reason for for the brief “flash” however as you will see from this thread it is currently not visible (“temporarily disabled”) in xps and pdf until you save the file as a different name AND load the file [with its .smx] in the official 3.1.2 release

I’ve re-enabled high-lighting in latest pre-release


great it’s working now! any chance of an annotation function also in the future, whereby you can double-click highlighted sections and add a note?

You can do that using Microsoft Windows and use SumatraPDF to read the Comments / Notes

This is similar to the technique used when editing a LaTeX file so the new 32 Mb limit applies for working with both applications on the same file

yeah MS works really well. Except, i’m trying to use open source software as much as possible, so it would be great if sumatra had these functionalities!

Windows is the native OS why replace core functions with Open Source :tongue in cheek:

SumatraPDF is MuPDf in a GUI wrapper so why not use MuPDF-GL as I suggest above which is the same core with annotation thus 100% compatible

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does muPDF-GL have a GUI?

and re WIndows, true, this is why i plan to move to Android as soon as a good privacy-safe, open source version is available cross-devices

I understand MuPDF has android version but dont know how Gooey it is and as for Google (I knowyour inside leg measurment) Android that is probable now a less private OS than Microsofts big brother one

haha true i agree on Google, but Android itself is open-source and there are many initiatives at work to develop privacy-safe, open-source alternatives to Google’s Android, e.g.