Hacking PDF to DWG


You’ve just gotten a Request for Proposal on a new project opportunity and with the supplied documentation are PDF files of the various drawings. As part of the RFP, you are required to supply your own drawings indicating how you would construct the project as well as enough information to establish a construction estimate. Thinking to yourself, “ I’ve got this one.  I’ve done this type of project enough to know the pain areas of the design.  The proposal documents are almost ready to go but I’ll blow the entire RFP budget on the drawings.  How can I stay on budget and win the project?

There are 2 ways to accomplish this. The quick and dirty way is to scan the PDF files and use them as image underlays in your file and “sketch” you design on top of them.  If your site is generally flat, then this may work for you from a quantity standpoint. but what if your site isn’t flat but built on a ex-military base where the average slopes are over 15%? Now, you need those contours to build a surface.

My friend, you will want to try the second method; actually converting those PDF files into DWG files. I know what you’re thinking, aren’t there add-ons for that sort of thing? Maybe, but what fun would that be? No sir, we are going the hard way to get clean and native elements in the DWG file. How do we do that? Adobe Illustrator to be exact. Wait, what? Who has that and what does it do?

Illustrator is the vector editor compared to Photoshop which is a raster editor. Most firms have a graphic artist who uses adobe applications, so cost shouldn’t be an issue. The steps are simple actually. Open the file in Illustrator and export to DWG. Seriously, that’s it, well almost. First, the PDF has to have been created directly from a CAD application creating a vector PDF. Secondly, there is one intermediate step. If you pick on line work, you will notice that everything is selected. Now right-click and choose “RELEASE CLIPPING PLANE” and now all of those elements are select-able individually.  That’s kind of like the AutoCAD equivalent to EXPLODE. You could then isolate and export objects by type as an option (Select>Same>Stroke Color).

Side notes about Illustrator.  Upon export, it will flatten everything to one layer. No worries, in most cases, it is simple to re-layer contours, utilities, etc. Also during the export process, it asks for how to scale the information. Be sure to use the noted scale bar on the drawing. For instance, if the bar indicates 1″=250′, then enter values in the scale dialog so it looks like this:

Now open that new file in Civil 3D, isolate the contours and build on. But further inspection shows the contours are all at elevation ZERO. So how do we get the contours up to proper elevation?  We have TWO options; either utilize Sincpac, which has a command called CHELEV (the trial will convert to a free edition containing this command), or you can use a LISP routine called CHELEV floating around the forums. Now we’re done?

If you were fortunate to have a grid on the drawing or some other coordinate system reference, then you can move the linework into correct position. In most cases for RFP work, location is not critical unless you need an aerial image to use for an underlay.

So just to recap the “hard” way:

  1. Open PDF in illustrator
  2. File>Export to DWG format; provide correct scale information
  3. Open DWG in Civil 3D
  4. Re-layer objects as desired
  5. CHELEV of contours to build surface
  6. Build surface and other Civil 3D objects as needed

That’s it!

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About Kevin
Hi… I am a husband, father, brother and neighbor. I am employed as a Civil Engineer and have enjoyed playing the drums for the last 30+ years.

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