in reply to Making Sudoku Puzzles Using PDF::API2
As has been pointed out, PDFs are based on postscript (PS). Postscript's line drawing functions (lineto, curveto etc) do "act like LOGO" in that the cursor moves; it surprises me that PDF line drawing functions have changed this.
Some excellent PS references are:
The PS tutorial and cookbook: http://www-cdf.fnal.gov/offline/PostScript/BLUEBOOK.PDF
The PS language reference manual: http://partners.adobe.com/asn/developer/pdfs/tn/PLRM.pdf
And perhaps best of all, Bill Casselman's "Mathematical Illustrations," which isn't amazingly cheap but is available free online at http://www.math.ubc.ca/~cass/graphics/manual/