INDUS,
Acrobat 4.0 generates pdf version 1.3, and that should be compatible with PlanetPress 7, as I tested it before and it works fine.
That said, the pdf file format can be tricky, as it contains PostScript code that is merged with our own PostScript code, and sometimes, this can cause some errors. A potential solution is to try to regenerate the pdf, and see if it works better. Try resaving the pdf from Acrobat, for example. Or do a Save As to a .ps, and use Distiller to generate the pdf.
Let us know if regenerating the pdf files helps.
Regards,
Rapha