because you bought it
Even though PDF is a horrible file format, it is well suited for textbooks since it can be opened virtually anywhere, often without needing additional software. Here are some ways to convert from proprietary, DRM-protected formats to PDF.
DeDRM_plugin.zipneeds to be edited, commenting out these lines:
if val406 != 0: raise DrmException(u"Cannot decode library or rented ebooks.")
As of 27 August 2017 it appears this no longer works because VitalSource is enforcing Bookshelf updates.
VitalSource Bookshelf needs to be installed, with the book to be cracked viewable in the Bookshelf program.
This program was my final resort in an exhaustive search, but sadly it stamped a huge red watermark on every page of the output PDF unless I bought it. After an investigation into the sorry state of PDF editors, I decided to edit the program itself. Luckily the author made a typo in the watermark ("Vitalsource" instead of "VitalSource") and I was able to track down the string to line 236340 of the
xxd dump of the
vbkdrm.exe file. By replacing the string with null bytes, the watermark can be circumvented. The patched version is available here.
Note that this only works with an old version of Bookshelf.
Not much experience here; the only book I got through this seemed to only be a PDF, but allegedly DeDRM as mentioned above supports this as well.