PDF image precedes mobi output for each page

[tcreek]

On a conversion from PDF to mobi for a Kindle 3, the mobi output is somewhat acceptable but a reduced image of each PDF page precedes the mobi output for that page. The original size of the PDF file was 5 MB but after conversion to mobi it was 121 MB. I reconverted from mobi to mobi with Heuristic Processing (not knowing what that is or does) and I have the same output but the file size is now down to 61 MB.

I still have a reduced PDF image of each page followed by the regular mobi output for the page, for all the pages of the book.

Is this one of those typical PDF anomalies? Easily fixable? If not, I will do without the book.