DRM protected PDFs can be a problem depending on the author/publisher and whether they are tagged. However, as a general rule PDFs and ebook readers don't go together, especially multi-column PDFs. Adobe never designed PDFs for reading on small devices. Adobe designed PDF nearly 20 years ago when most people didn't own a computer. It was really designed as a secure way to pass an electronic file from one person to another--as in legal documents, business documents, etc. PDFs originally were not designed to be viewed on an electronic device as much as they were designed to be portable and printable. In the 19+ years since PDF was designed we have evolved from a world wherein most documents were printed and read to a world wherein documents are likely to be read on some kind of electronic device like a computer, smartphone, ebook reader, etc. IMO Adobe never adequately adopted the PDF for that purpose, so it is a terrible document format for electronic devices. Bottomline, don't expect a PDF to look decent unless it is printed out. some will look okay on an ebook reader and they will reflow, but many will look like garbage even if converted.