You can try something similar to Amazon's conversion by importing a DRM-free PDF into
Windows MobiPocket Reader. This converts the PDF into a MOBI ebook. Amazon started with MobiPocket's PDF to MOBI software, but may have improved it in some cases (I think it now does a better job of converting non-text pages into images). You can obviously also try Calibre's conversion.
These "full document" conversions have some advantages over Adobe's page by page conversion, but one issue with full document conversion is that it is hard to reliably strip headers and footers from each page. Calibre want you to define a regular expression to identify them - a good approach if you know regular expressions but otherwise a hassle.
If you send your documents to the free e-mail address at Amazon there is no charge, but the download is via wifi only.