Add WYSIWYG
Currently the Proton Doc editor is not WYSIWYG (What You See Is What You Get) : once you click on "download" or "print", the document looks totally different from what you were editing (also, the editing view misses a page boundaries display).
Moreover, the "download as pdf" gives a totally different look than the "print as pdf" (MacOS) option.
It makes it really hard, if not impossible, to use Proton Doc to build PDF documents or to print ones.
Google Docs manages to do that so it should be possible to do it in Proton Docs as well.

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TheLorax commented
I also have a problem with this. Saving as a docx then opening in Word365 or in Pages (Mac) makes the formatting totally different from what I see on ProtonDocs.