Amazon has announced two new enhancements to its electronic-book reader Kindle, which includes an 85% more battery life and a native PDF reader.

With these enhancements Kindle is expected to have battery life of up to seven days even with wireless turned on, compared to its previous battery life of four days. The battery life with wireless turned off remains at the previous level of up to two weeks, the company said.

Amazon said that the built-in native PDF reader in 6-inch Kindle enables users to read professional and personal documents in their original PDF format without conversion. To read documents, users have to email PDFs to their Kindle email address or move them over using a USB connection. To convert PDF documents to Kindle format, users have to type ‘Convert’ in the subject of the e-mail when sending documents to Kindle email address.

Ian Freed, vice president of Amazon Kindle, said: “Kindle, already the #1 bestselling, most wished for, and most gifted product on all of Amazon.com, is now even better – with 85% more battery life and a built-in PDF reader. These two significant enhancements are available now.”

Previous purchasers of the new Kindle will also receive the new enhancements through a firmware update automatically delivered through Whispernet wireless. Native PDF support will also be available for some earlier versions of Kindle, the company added.