The Key to Using PDF in AutoCAD

[nrdgrl]

If you receive a PDF file and want to use it in AutoCAD, you first need to determine what type of file it is - vector or raster. Once you know this, you can pick the correct tool for a successful conversion.

Determine PDF type by opening the drawing in Acrobat. Magnify a section of the drawing to >800% and eyeball it. Try and zoom in on an area with curves if possible. if the highlighted area looks smooth and crisp, it is a vector PDF file and the you should use an extraction tool to render the drawing in an editable CAD format such as DXF or DWG. This approach is both reliable and accurate. On the other hand, if the zoomed drawing looks pixelated, grainy, noisy or jagged, it is a raster PDF file - most likely a scanned drawing. For this type of file, you need to manually redraw or try raster-to-vector tracing software. Results are variable and depend very much on the quality of the input. Most people get both types of files and should have tools at hand for both vector extraction and raster-to-vector conversion. Raster-to-vector solutions should never be used on vector PDF files. It's much less accurate and should be limited to use on scanned drawings.

Spotting the Difference - Vector and raster PDF
http://visual-integrity.com/support/...or-raster-pdf/