When converting plans from an image file like PDF to a vector file lile DWG you run into two major problems.

First is time. The conversion process requires that you import the image as an image and then trace over every line on the plan. This is very time consuming and therefore expensive. Software is out there that can automate some of this process but the problem is accuracy, the software often will induce errors that you must find and correct. All of this takes time and money.

The second problem is errors in the plan itself. It used to be when I built from plans some of the parts didn't fit quite right. I assumed at the time that the error was mine and that I didn't cut the part out accurately, maybe I cut to the outside of the line instead of the middle or inside of the line. When I drew my first pan in CAD I discovered that the problem is the plans themselves. They contained errors and plenty of them, and they all needed to be corrected.

If you send a PDF file to a laser cutter and the parts don't fit properly you will likely blame him for the errors. If you send a DWG file there will be no one to blame except the person that created the DWG file. Much safer for them.

I once considered entering the kit business and had a draftsman convert a small .15 size plane from PDF to CAD so I could have it laser cut. The charge was around $500 for his time.

Why not do like I have, learn a simple CAD program like DeltaCad and draw the plans yourself?