Freeform won't allow me to insert pdfs the same way as it used to

First, let me apologise for having to post in "Other Apple Applications and Services" as there doesn't appear to be a more appropriate forum.

When Freeform first appeared I used it on a project (up to January 2023) where I could insert a pdf from anywhere on my Mac using the "insert picture" tool. It then showed up as a fully rendered vector preview without a grey file bar at the bottom, and I could draw over it directly in Freeform. I still have some of these boards, and when I select the pdf it shows the tools for an image – not a file.

If I click "Replace" I can no longer choose a pdf – only photos from my Photo Library. I can't import pdfs into my Photo Library…

Is this functionality that came and went? It was really useful – I don't want to markup a pdf in Preview as it lacks all the useful drawing tools Freeform added, but it seems that's now the only option?