well here's a strange one, with a simple work round
opened a pdf in illy cs2 recently - all went well, no major surprises and even no font issues.
so there i was applying traps to elements - not harming anyone, just trapping away - and i had some spot text to spread. only - it wasnt as simple as stroke and overprint.
the element was uneditable. it wasnt linked, embedded, grouped, locked, on locked/hidden layers or anything. it was as if it was there - but wasnt really - illustrator was just kidding....i could move it, scale, rotate - do anything except edit.
it would not expand, there was no mask to release - nothing worked - it was plain wierd. yeah - i could rasterize it, but it was spot so no good. live trace and paint didnt work either.
i tried everything I knew (at that moment in time)....
solution: copy element, paste as PATH into photoshop (yeah ILLY - Photoshop can see the paths - why the frell cant you!), select all path, copy again, and paste back in illy "in front/behind (if you need to keep original illy element that is) and viola - editable paths! stroke applied, overprint applied, new knowledge gained.
next!
