Discard diagonal text.
void pdfSetDiscardDiagonalText(int discard)
XpdfText normally splits characters into four groups, with 0, 90, 180,
and 270 degree rotation. That's useful for the common case where a
small amount of text on the page (labels on a graph, for example) is
rotated 90 degrees from the main text. It also handles the situation
where some text is drawn at a diagonal, as long as it doesn't overlap
any other text.
If this function is called with a non-zero argument, XpdfText will
discard all text that isn't within a few degrees of one of the
0/90/180/270 degree axes. This can be useful for cases where diagonal
text overlaps main body text (e.g., watermarks).
This setting is global - it applies to all PDF handles.