Damaged files when extracting figures

Why my .pdf and .ps files are getting damaged, when i extract figures to them? I've tried all the commands (hgexport, print etc) and when i extract figures to them, they get damaged, they can't even open, and their KB size is reduced to something like 2 to 7 KB. I also tried to extract in all the ways e.g. to an existing file, to a new file, to an empty file, to a not empty file etc..and i get the same results..My upper aim is to extract multiple figures from a loop into one pdf, and i cant extract even one by one..Thank for your help!