Amazon’s Personal Document Service has maintained a $.10 fee for every document transferred via Whispernet since the device was launched, but the service will now cost at least 50% more. Starting May 4th, Amazon will charge $.15 per megabyte rounded up to the nearest whole megabyte for each document transferred. Basically, the base fee will soon be $.15 and it goes up from there. It’s not all sour grapes though.

The service will now support RTF files fully and DOCX on an “experimental” basis. That means that some DOCX docs might not render properly just like some PDF files. Free transfers can still be performed just like always by emailing the document to the appropriate address for conversion. This fee is only when files are transferred over the air.