The free viewer, markup and measuring tool - Autodesk Design Review - allows to add also drawings in the PDF format to its projects and project books (DWF/DWFx).
By default, this application uses a rasterization method to load and interpret PDF files (of both raster and vector types). This method has limited precision and does not allow to use osnaps (snap to geometry objects) in the contents of PDF files (e.g. for measuring or markups).
But Design Review 2012 and 2013 support also vector processing of PDF files (coming e.g. from AutoCAD or other CAD software). You can switch the processing mode using the Windows Registry.
Run REGEDIT and in the key:
(for Win7/Vista), or in:
create a new DWORD value PDF Conversion Method and set it to the value of 2. Run Design Review again, insert a PDF file (e.g. by mouse dragging) and watch a different way it is displayed while zooming. Now you can also use osnaps, e.g. to intersections or line endpoints.
While rasterized DWFs store the PDF contents as a TIF image, vector DWF stores it as a 2D-stream.
Of course, the resulting file can be saved back to a DWF/DWFx file so Design Review can act as a vector PDF to DWF translator.
Credit: W.Tank, Autodesk, 4/2011