> I have been looking around and I am not sure how to solve this
> problem. Withing Evince and Xournal I am encoding any non alphanum (as
> defined by the C macro) each byte that is contained in the filename
> individually.
> 
> Does anybody know which are the characters above 0 (zero) that need to
> be encoded for a safe org link? 

AFAIK, your current approach is correct.

I think I figured it out for evince: the file name you get from evince
is already URI-encoded.

The attached patch fixes the problem for me, but I do not know if it is
the right thing to do. I assume that the forward slashes in the file
name still have to be encoded so that org-protocol is not confused; the
patch disables URI-encoding for percent signs, so that already
URI-encoded characters pass through unharmed.

- Jan