Just because it “Works For Me!” does not mean it will work.
Beeper very much does not currently allow new users to access the functioning legacy iMessage infrastructure; and Apple itself is making it impractical as well.
From the Beeper Community chatroom on Matrix:
[iMessage] Important Notice.
Beeper no longer provides support for iMessage-related issues.
It has become known that Apple has targeted users of legitimate Mac computers for using Beeper to generate iMessage registration data. Beeper has commented about this situation on Twitter/X here and coverage of this issue has been reported in the New York Times here.
As a result of this media pressure, many of those affected have been successful in having their hardware bans lifted. If you are still affected by a ban that you believe is related to generating a registration code on a Mac computer to use iMessage through Beeper please report it to Beeper Help here and please contact Apple Support as well.
As of this time Beeper has removed support for iMessage from Beeper Cloud due to Apple’s actions. It is suggested that those still using registration data generated from a Mac computer to access iMessage through Beeper delete their existing iMessage bridge in Beeper Cloud.
For any further questions related to iMessage please visit our helpful Discord community.
I’m sorry to say; but that feature genuinely does not seem to exist in any Open Source PDF reading/editing application.