We are planning to release more export options in the coming months, but no dedicated PDF export is planned at the moment. However, it's something that could be relatively easy to achieve using a dedicated plugin. (We can discuss it in more detail when export plugins are ready).
As for importing from PDF, we already have a few ideas in mind. Would you be looking for a way to import all the photos in the PDF as single photos (which you'd then organize to items) or does each PDF document represent an item, or otherwise, a context which you'd like to be able keep in Tropy (i.e., would you like to be able to see, in Tropy, from which PDF file, page, etc. the photo comes).
(Note that for the first scenario, there may already be an easy path to get the photos into Tropy by using a tool such as
pdftoppm to extract the photos from the PDF and then import them into Tropy).