New User

I did use AutoCAD, more than 15 years ago gave it up as the cost per use made no sense.  Have tried to retire, I may be failing.  Many of my contacts, architects, engineers, and designers, have been asking for some help in some of the concrete construction details and I will need to import their DWG files and work out the details and could export in PDF.  Is their another format to export format that AutoCAD would read and simplyfi the transision?

Well, the support of DWG in LibreCAD is quite limited. So the more promising way in your scenario will be as following:

1) existing dwg are exported as dxf (either using AutoCAD or via some online services - there are tons of them nowadays, like https://cloudconvert.com/dwg-to-dxf or https://cad.online-convert.com/convert/dwg-to-dxf or any other suitable, you may simply find them with google).
2) these dxf may be opened by LibreCAD
3) you make necessary modification there
4) save/export to pdf.