I'm going to delay until 92. Bug 1726789 was brought to my attention and I don't think I'll have time to fix that before 92 release.

Release Note Request
[Why is this notable]: We now support filling more types of PDF forms (e.g. Canada government forms), which means users will not have to leave Firefox to fill them.
[Affects Firefox for Android]: No.
[Suggested wording]: Firefox now supports filling most PDF forms.
[Links (documentation, blog post, etc)]: There will be a blog post, it is not available yet.

(In reply to Marco Castelluccio [:marco] from comment #2)

Release Note Request
[Why is this notable]: We now support filling more types of PDF forms (e.g. Canada government forms), which means users will not have to leave Firefox to fill them.
[Affects Firefox for Android]: No.
[Suggested wording]: Firefox now supports filling most PDF forms.
[Links (documentation, blog post, etc)]: There will be a blog post, it is not available yet.

Any reason not to reuse the wording we had planned for 92?:
https://bugzilla.mozilla.org/show_bug.cgi?id=1706133#c4

Firefox PDF viewer now supports filling more forms (XFA-based forms, used by multiple governments and banks).

My bad, I copied the original comment with the old wording.

Note added to 93 beta (will be visible on https://www.mozilla.org/en-US/firefox/93.0beta/releasenotes/ shortly)

XFA support is currently behind the "EARLY_BETA_OR_EARLIER" flag:
https://searchfox.org/mozilla-beta/source/modules/libpref/init/all.js#353-356

That means that the feature will be deactivated after 93 beta 6. Since the decision to ship in 93 seems to be taken can we make sure that we have that ifdef removed on mozilla-central and uplifted to beta? Thanks

https://hg.mozilla.org/mozilla-central/rev/e6a484037f3d

Comment on attachment 9240661 [details]
Bug 1727396 - Enable XFA support in the PDF Viewer in 93 release. r=#pdfjs-reviewers

Beta/Release Uplift Approval Request

• User impact if declined: XFA PDF forms will not be enabled.
• Is this code covered by automated tests?: Yes
• Has the fix been verified in Nightly?: No
• Needs manual test from QE?: No
• If yes, steps to reproduce:
• List of other uplifts needed: None
• Risk to taking this patch: Low
• Why is the change risky/not risky? (and alternatives if risky): Only turns on pref by default.
• String changes made/needed:

Comment on attachment 9240661 [details]
Bug 1727396 - Enable XFA support in the PDF Viewer in 93 release. r=#pdfjs-reviewers

Planned uplift approved for 93 beta 6, thanks

https://hg.mozilla.org/releases/mozilla-beta/rev/3e396769ef26

I can confirm that the "pdfjs.enableXfa" pref is true by default in Beta v93.0b8 and Nightly v94.0a1, while it is false by default in Release v92.0 and ESR v91.1.0esr.