Free editor for PDF documents. Complete editing of PDF documents is possible with PDFedit. You can change raw pdf objects (for advanced users) or use many gui functions. Functionality can be easily extended using a scripting language (ECMAScript).
GeekCAD is a free open source CAD system. It's based on Qt4.
Features of this project:
1. dxf import, export;
2. raster bitmaps export;
3. native postscript or pdf export (in future);
4. Python scripting;
5. Parametric drawings.