Okay, well, here's what I think has happened.
When the PDF file was uploaded to the server, it appears as though it was compressed. The file would upload to the server but only be about 3.8MB instead of the 4.9MB it should have been. But when I downloaded the file from the server it seemed to have expanded it. So perhaps the problem people are having is with the decompression during the download.
So, I have ZIPped up the file and uploaded it. THAT upload came across without descrepancy in the file size. So I am hopeful that when people download the ZIP file, they PDF inside will be intact.
For those of you who still don't have a good download after purchase, please email me .