The ‘save’ operator takes a snapshot of the state of the PostScript interpreters memory.
PDF files have a limitation in the number of ‘save’ commands that can be nested (16 levels I think). From time to time, I run into ‘limitcheck’ errors, offending command ‘save’ when trying to output PDF files. Exporting the PDF to a PostScript file and then redistilling that file again got me around the ‘limitcheck’ error the last time I encountered it.
One visitor reported that a PostScript error, offending command save was caused by a corrupted image on the page. Replacing the image solved the problem.
Nesting files (e.g. putting an EPS in another EPS, placing that EPS on a page, exporting the page to PDF to put it on another page and then saving that final page as a PS-file to impose it) can also lead to ‘save’ errors. Avoiding excessive nesting while creating or processing documents is always a good idea. Since it is sometimes impossible to know which images or other elements already have other files embedded within them, selectively deleting elements and reprinting the document is sometimes the only way of finding the bad element.