Auto-reload of pdf no longer works


One of the key advantages of SumatraPDF over the other pdf readers is the ability to auto-reload the PDF when it has been modified externally (by other applications).
However, I found recently that this no longer works, but I’m not sure why. It used to work before.

Reproducing the error:

  1. Open file.pdf in SumatraPDF. (file.pdf is in my Desktop)
  2. Open file.pdf in Adobe Acrobat Pro.
  3. Highlight a line in file.pdf in Adobe Acrobat Pro (or just make some changes).
  4. Save (Ctrl+S) file.pdf in Adobe Acrobat Pro.

Then an error pops up, saying

and I am unable to save in Adobe Acrobat.
It (saving) only works if I close out of SumatraPDF first.

This seems to suggest that SumatraPDF is hogging on to the file.pdf, which is not supposed to be case. Normally, SumatraPDF auto-updates the file when it has been modified and saved externally.

Also, note that

ReloadModifiedDocuments = true

is set in my advanced options.

Any help will be appreciated.

I am on Windows 10, 64 bit, running Sumatra v3.1.2.


Look at the file size, its most likely at this point about or over 10mb (with your additions?)

SumatraPDF has a threshold around that level, If you need to change it you need to modify the source code and recomplile your own variant or add to the existing requests in github “issues” to make it a user variable


Yes, you’re right. It is 13mb after my recent additions. Thanks for the notice regarding file size, I didn’t see it anywhere else (or perhaps I missed it in the docu).