Hi, thanks for your reply.
I open an existing PDF file in Affinity Designer end edit something and re-export this file as PDF without things like bleed and co. Just the pure and unchanged workspace. However, I get a larger workspace in the output by a few pixels on the bottom and right side.
I don't have that phenomenon when I go the same way in Illustrator, for example. I have had this problem several times with Affinity Designer sometimes it appears sometimes not.
I have made several tests. Also once where I just turned everything off in the advanced export options. However, I always get unwanted free space at the bottom and right.