I have a pdf in my database in DTPO 1.3.4. I opened it in Preview (Leo Version 10.5.1). Then I delete some pages, saved, and close the pdf.
Aftewards, I watch the pdf in my DTPO database, but it is the old version, the deleted pages included. But, then I opened the pdf in Preview again and: It shows me the pdf without the pages I had deleted before.