We've mentioned Lineform a couple of times, but the newly released version 1.3 of Freeverse's Illustrator alternative vector illustration program adds a significant new feature: PDF import and editing. You can now directly import a PDF into Lineform, resize it, and mark it up with the standard Lineform drawing tools. Other new features include improved SVG support and 256000% (!) maximum zoom.
Lineform remains $79.95 and a demo is available.
[Via Daring Fireball]