Lynn Allen, Cadalyst contributing editor and Autodesk Technical Evangelist , presents a useful video for AutoCAD professionals. In this video tutorial, Allen provides some useful cad tips to transform PDF files (underlay) to AutoCAD objects.
So, the AutoCAD users can get rid of time consuming tracing on top of PDFs to reproduce objects or draw it from the beginning.
You can import the objects in a PDF file or PDF underlay into your current drawing file.
Import the Data from a PDF File
- Click
. 
Find - In the Import PDF dialog box, specify the PDF file that you want to import, and click Open.
- If the PDF has multiple pages, choose the page to import by clicking a thumbnail image or by entering a page number.
- Choose any of the options and click OK.
- Specify the insertion point if prompted.
Import a Specified Area from a PDF Underlay
- Select the PDF underlay.
- On the PDF Underlay contextual tab, Click Import as Objects. Find
- At the prompt, click two diagonal points that define a rectangular crossing area, or choose one of the other options.
A crossing area is similar to a crossing selection. The Settings option displays a dialog box in which you can choose what types of objects to import, how layers should be accommodated, whether the imported objects should be imported as a block, and several other options.
- Choose whether you want to keep, detach, or unload the attached PDF after the selected objects have been imported.
The specified area of the attached PDF is imported into the drawing as AutoCAD objects.
For more details, watch the following video tutorial.