Amazon has announced that they will be introducing a couple of changes to their Kindle Personal Document Service on May 5, including a modification to their pricing structure and supported file types. The fee associated with transferring personal documents wirelessly to the Kindle will be based on the file’s size.

Sending personal documents via Whispernet will be $0.15 per megabyte, and rounded up to the next whole megabyte. In order to download personal documents without charge, users can continue to send attachments to their free.kindle.com address to be converted and forwarded to their Amazon account email address.

In addition to the list of presently supported file types (DOC, HTML, JPEG, GIF, PNG, BMP, AZW, MOBI, PRC), users will be able to send Rich Text Format (RTF) files to their Kindle email address for wireless delivery. Also, although some files may not be formatted correctly on the Kindle, users can now partake in converting their DOCX files in addition to the experimentally supported PDF file type.