We have an application that generates PDF files using Quick Report library.
Those PDFs cannot be edited in Adobe Acrobat 2020 (Adobe Acrobat has encountered an unknown error) but they can be edited with other PDF tools such as SodaPDF.

I tried all methods listed in this forum but nothing worked.

The only solution is to print the PDF using the 'Adobe Printer' and then edit this file.
It's a simple workaround but quite painful when you have to do it dozens of times per day.

It would be nice if Adobe could provide a fix for an issue that has been happening for years.