Join Date: Dec 2008
Location: Perth, Australia
Device: Sony PRS-650, Sony PRS-T1, Kindle 3, iPad2, Nexus7v2
If you are buying ADE ebooks you would need to register your reader with Adobe via the Adobe reader software. You can also use Calibre to transfer the ADE ebook to transfer to your PRS-300 but you cannot convert the ADE ebook to another format without using third party tools to liberate the book from DRM.
You certainly can buy from Borders. I have purchased a few books, removed DRM and used Calibre to transfer to my PRS-300.