JWP1938,
Pretty much what you've already been told....
If your PDF files are too big, then nine times out of ten, its your fault, not the PDF file format.
What software are you using to generate PDFs ?
If Adobe Acrobat, check your settings and perhaps also use the built-in optimizer function.
If not Acrobat, Google "PDF optimizer" and try out some software such as Apago PDF Shrink.