There is experimental support for PDF files through PDF.js (see Tools / PDF viewer), but there's no direct connection to machine-related documentation. The interest/priority to complete this functionality is low at the moment because it's not clear yet if this approach will still work when we switch to Qt 5.
EDIT:
The alternative would be to use
Poppler, but I hate its many dependencies (although everything should be available on Windows and probably Mac OS X as well). Anyway, external dependencies should always be an optional thing, so that's why I decided for PDF.js in the first place (it can easily be integrated, Mozilla Firefox does the same BTW).
Right now there is no external dependency besides Qt 4 or 5.
- SDL is required for joystick support but can be disabled
- libarchive can be enabled if available but is not required
- zlib, lzma and minizip are 'bundled' but can be switched to external libraries (system-libs)
I would like to keep it that way. So PDF.js seems to be the only solution unless Qt 5 gets built-in support for PDF rendering.