Hi @Ste_W
Of course the best hosting solution is the one that is affordable and accessible to you. I can’t say what’s best for someone else, but I use dropbox (since I’ve long had an account anyway).
Even though dropbox isn’t really aimed at hosting for the web, you can do it with “this one simple trick”:
Dropbox tells you the url for a file (thinking you’ll put it in an email or something), and it looks like this:
https://www.dropbox.com/LONGSTRINGSTUFF.pdf?dl=0
The link lands you at a dropbox-managed view/preview page.
But if you replace the final dl=0 with raw=1 then the link is suitable for use as the _canonical_uri field of a tiddler with type application/pdf.