so i put timestamp with my document folder so mypath look like this:
/Users/zee/Library/Application Support/iPhone Simulator/6.0/Applications/10EF6B94-0ECD-484A-AF5A-D300D8EF55DB/Documents/myPDF.pdf1382698338.78128
You should try using a different scheme for naming you files, so that the extension is kept unmodified, i.e.:
..../myPDF<TIMESTAMP>.pdf
e.g.
..../myPDF1382698338.78128.pdf