The office I work in does very little 3D work. So we're primarily a 2D shop. Were constantly trying to take consultants 2D files and overlay them in ours. Well a lot of the times they wont send us DWG files, or they are on some CAD drafting application from Mars? You know how it is. So how do you get someone else's data into your files to update if you have no DWG's? Well no more wondering, you got DWFATTACH. DWF Attach allows you to browse and insert a DWF into your AutoCAD drawing as a DWF Underlay. You can import multi sheet DWF's and select which sheets to underlay. The precision is pretty good, but depending on how precise you want, depends on what the DPI setting of the DWF was plotted out at. So if you need EXACT, then you might want the DWG. If you need relatively close, or reference/ trace over, then DWF is the way to go. You can snap to geometry, clip the DWF, and change its contrast. (You CAN NOT however translate geometry from the DWF to the DWG unless you manually trace over all the lines, So your security of your DWF's are still kind of there.)
Inside AutoCAD 2007 you can enter DWFATTACH and simply browse for a Multi Sheet or Single Sheet DWF. Once you've selected your DWF you can then choose which sheet you would like to import, or select other options such as Path type, Scale, Rotation and Insertion Point. Pretty much the same options you see when attaching an Xref.
Note: One option many will probably be asking for is Layer control. Currently this is not supported and does make using the underlay a little bit hard to use. But if its a simple underlay it should work pretty good.
Here is an image showing some of the options you have when importing a DWF as an underlay. You can adjust the Contrast, Fade intensity, toggle the DWF between Monochrome settings, and Adjust its colors. Adjusting its colors helps you see the DWF with the type of background color you have.
What about getting a PDF into AutoCAD?
With the growing numbers of users out there using DWF, the majority are still transmitting with PDF. So what if I don't have a DWF and want to import a PDF? Well you can!! Just takes one extra little step. First step is to open your PDF inside Adobe Acrobat. Next you need to make sure you have the Free Autodesk DWF writer installed. Next simply plot your PDF to the DWF writer to create a DWF. Next just use the DWFATTACH command and simply browse for the newly created DWF to import your DWF into your DWG as an underlay. So now you can import not only DWF but PDF using the free Autodesk DWF writer.