AFAIK - during any Browser crash unless the site your using saves as you work most times the filed or site opened is lost since the Browser didn't have a cache saved of the site or files itself to recover from. It's best advise to constant save the files where your working on the site to prevent unforseen crash happening and there are many reason why it happens so there is no one reason to it as well.

It would be better if Firefox saved your changes in the built-in PDF viewer as you worked, but as far as I can tell, it doesn't. Unfortunately, I don't think there are any add-ons that can do it, either, since they are restricted from accessing the innards of the built-in PDF viewer.

Mozilla has a product suggestion site at https://connect.mozilla.org/. I think if you have time, it would be a good idea to post this request there to get into the current feedback stream. Use the "Ideas" section of the site.

If you haven't saved the file then it is likely that your edits are lost. If you regularly experience crashes then best is to save your edits at regular intervals.

Did Firefox crash or was there another problem on the laptop?

If you have submitted crash reports, please post the IDs of one or more recent crash reports that start with "bp-".

• bp-xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx

You can find the report ID of recent crash reports on the "Help -> More Troubleshooting Information" (about:support) page.

• click the "All Crash Reports" button on this page to open the about:crashes page and see all crash reports.

Alternately, you can open about:crashes via the location/address bar.

See also:

• https://support.mozilla.org/en-US/kb/mozillacrashreporter
• https://support.mozilla.org/en-US/kb/troubleshoot-firefox-crashes-closing-or-quitting
• https://support.mozilla.org/en-US/kb/firefox-crashes-asking-support