( resource p, string key, string val )
Sets certain information fields of the document. This fields will be shown
as a comment in the header of the PostScript file. If the document is
converted to pdf this fields will also be used for the document
The BoundingBox is usually set to the value given to the
first page. This only works if ps_findfont() has not
been called before. In such cases the BoundingBox would be left unset
unless you set it explicitly with this function.
This function will have no effect anymore when the header of the postscript
file has been already written. It must be called before the first page
or the first call of ps_findfont().