I have seen problems with corrupt pdfs (that particular filetype). I would recommend zipping the files and delivering the zipped file if possible. I also notice that some pdfs are reading as corrupt when authored in one version and opened in another of adobe acrobat.

"This type of problem is most likely to occur when attempting to load a PDF document which is larger than .5 MB, OR when attempting to load a newer PDF document with an older Acrobat® viewer -- i.e. when attempting to load a PDF created with the version 3.x tools, with a version 2.x Reader.

NOTE: It is extremely rare for the source PDF document (the file from the server) to be corrupt. Once the originals are created and tested (and placed on the server), the only corruptions which are likely to occur, would be due to physical hardware problems (bad sectors, etc.) on the storage system itself. THE SERVER simply sends files requested by the user - it does NOT contol how the document is saved, stored, viewed or otherwise manipulated on the local PC.

Most PDF file corruptions occur ON THE USER's LOCAL PC, as a result of a failure in the Browser/Plug-In Applet. "