Amazon this week announced some changes to its Personal Document Service, with the biggest one coming to its fee structure. Starting May 4th, no longer will it cost a dime for every document Kindle owners send to their eBook reader (via Whispernet, the Sprint-based EV-DO network that delivers books and user conent to the Kindle), where they're automatically converted for viewing. Instead, Amazon is switching to a consumption-based billing model and will charge 15 cents per megabyte, which will be rounded up to the next whole megabyte.

The other change is the addition of RTF and DOCX file formats. These will be added to the current supported file types, which includes DOC, HTML, JPEG, GIF, PNG, BMP, TXT, AZW, MOBI, and PRC. PDF documents are also somewhat supported, although Amazon warns that "Some complex PDF and DOCX files might not format correctly on your Kindle."

For those looking to avoid fees altogether, Amazon reiterated that users can still send their personal documents as an email attachment to "name"@free.kindle.com, where they will be converted and emailed back to the recipient free of charge.

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