Solid 10. Bluebeam was designed for the AEC industry. It's way cheaper than Acrobat Pro and 10x as effective.
PDF creation, markup, editing and collaboration for an all digital workflow. Includes direct plug-ins for AutoCAD®, Revit®, Navisworks® Manage, Navisworks Simulate, SolidWorks®, and Microsoft® Office, for one button PDFs (2D&3D) and batch creation.