I've been using the Universal Document Converter for years now with Carlson Survey and have been quite happy with it. If you go on their website they should still offer a free download which is fully functional except that it leaves a watermark on the file. Last time I had to upgrade/ reload the program it cost about $40, so it's not a very big investment.
Any pdf viewer with pdfcreator will do the same thing.?ÿ https://www.pdfforge.org/pdfcreator
The new version has a dialog that allows you save in many different formats including png which I find works best in Autocad.
If you're using AutoCAD 2018 or newer, they read PDF files now. You can even scale them and snap to lines within the PDF.
T. Nelson - SAM