I'm sharing my experiences with PDF till now.
1. I would recommend formats like epub or txt or docx or odf or just
an 'offlined' html (without the excessive supporting files that a
normal browser Save creates). The pdfs become closed fortresses;
they're good for printing and protecting, for saving to print later;
not for reading and sharing.
2. We can't read them properly on a phone (have to drag left and right
all the time to read sentences). And some kinds of phones can't open
them whereas text files they can.
3. On a new computer and some makes of android devices, you have to
install software to run a pdf; and Adobe which really infests the
system with background updaters is the most prominent one available
(don't expect our target audiences to know about alternative
4. They usually weigh more than the same content would in other formats.
5. The content in them can't be efficiently copied over to quote in
papers and excerpts. We want the content to be open, not closed. I'd
love to see college students copy-pasting from the stuff I'm sharing
and mixing them into their papers and submissions. I want to enable
6. They're not machine-friendly, so programs can't index them or
extract useful information from them. This is why Project Gutenberg
(largest repository of ebooks in open domain) insists on using simple
text files instead of pdfs. Content going into pdfs is more likely to
be forgotten and lost as compared to other formats.