Positions relative to certain common points can be set:
No attempt is made to take account of the page rotation when interpreting the position, so -prerotate must be added to the command line if the file contains pages with a non-zero viewing rotation. This is equivalent to pre-processing the document with -upright.
The -relative-to-cropbox modifier can be added to the command line to make these measurements relative to the crop box instead of the media box.
The default position is equivalent to -topleft 100.
The -midline option may be added to specify that the positioning commands above are to be considered relative to the midline of the text, rather than its baseline.