[Affected versions]:

• Firefox Nightly 83.0a1 (Build ID: 20200922154306)
• Firefox Beta 82.0b2 (Build ID: 20200922183749)

[Affected Platforms]:

• Windows 10 x64
• Mac 10.15
• Linux Mint 20

[Prerequisites]:

• Have the Firefox browser installed.

[Steps to reproduce]:

1. Open the Firefox browser and navigate to the https://pdf.ninja/interactiveform_enabled.pdf page.
2. Check any checkboxes/radio buttons.
3. Select the “Print” option from the Hamburger menu.
4. Select the “Landscape” option from the Print preview panel.
5. Change back to the Portrait orientation.
6. Observe the checkboxes/radio buttons from the Print preview.

[Expected result]:

• The checkboxes/radio buttons are ticked.

[Actual result]:

• The checkboxes/radio buttons are unticked.

[Regression]

• The issue is not reproducible with older Nightly 82.0a1 builds. Considering this, using the mozregression tool I have found the issue that broke this in the latest Nightly build. Here are the results:
• Pushlog: https://tinyurl.com/y4hyxoz8
• Last good revision: aab5984f73dbf4b92704d1101def62e2a395f6ea
• First bad revision: a8044f7381bfcda31e11f4671f39838345d6b076

From this pushlog it seems that Bug 1665178 introduced this behavior.

[Notes]:

• The issue is also reproducible in the following cases:
• If the print preview is closed and reopened.
• If the Pages -> Custom option is set.
• This issue is not reproducible for the editable fields from the PDF.
• Attached a screen recording with the issue.

A patch is in review:
https://github.com/mozilla/pdf.js/pull/12414

I have verified this issue using the latest Firefox Nightly 83.0a1 (Build ID: 20200927215113) on Windows 10 x64, Ubuntu 20.04, and Mac 10.15.

• The checkboxes and the radio buttons remain marked after the print preview page is modified.

https://hg.mozilla.org/releases/mozilla-beta/rev/8319e9cd6b16

I have verified this issue using the Firefox Beta 82.0b5 (Build ID: 20200929175845) on Windows 10 x64, Ubuntu 20.04, and Mac 10.15.

• The checkboxes and the radio buttons remain marked after the print preview page is modified.