It appears that evince on X11 systems is using the physical display size reported by the Xserver at startup (the "dimension") to determine DPI for rendering. Unfortunately, that size is almost always a lie, modified by the server to give a default DPI of 96 regardless of the physical DPI. Instead, evince needs to query the XRandR extension, when available, to get the physical display size for the current mode, and use that in its DPI calculation. If it does this, it will render at accurate physical size for most displays.

Reproduce by: render a PDF with known physical dimensions on an X display with actual physical DPI not 96. Get out a ruler. Verify that the physical size of the rendering on screen is wrong. Even after correcting the DPI, there may be problems due to the mishandling of fractional DPI (bug #693428).