Unable to open old pdf files using FrameMaker

[Daniel23403969q75s]

When trying to open old pdf files in FrameMaker - the thumbnail fields are empty.

[Creamer Training]

FrameMaker doesn't "open" PDF files. You can import it as a graphic but cannot edit it.

Can you give more info as to your goal?

[Bob_Niland]

If you have a PDF reader that can export to RTF or other authoring formats, try that. I just verified that it mostly works, using Acrobat Pro DC to
open a PDF 1.6 (PDF/A) document,
Enable Edit,
File » Export to » RTF,
then opened in FM2020.

As David points out, PDF is not an authoring format, but there are many ways to perform content recovery for on-going maintenance & republication.

[K.Daube]

When trying to open old pdf files in FrameMaker - the thumbnail fields are empty

When importing - not opening - PDF files and they do not show something in FrameMaker, then there is no preview image in the PDF. Open the PDF in a PDF viewer to see what's in it. If output is created from such an FM file which has imported PDF, you will see the contents of the PDF also.