Saved PDF files are unreadable

I want to use my iXpand to save created PDF files at my iOS devices and print them at our printer at work.

I tried many apps (Word, PDF Expert, Mail app, Notability, …) but on iXpand the saved files are unreadable.

Sometimes I can open them but they have illustration errors or are completely empty.

The printer won’t print any of these files.

What can I do?