Hi @Michael Feehan,
Thanks for reaching out to us. We are very pleased to support you.
Unfortunately, SharePoint does not currently have the ability to set up automatic checkout of files when you open AutCAD & PDF Files. Auto-checkout is currently only available for Microsoft Office documents.
SharePoint being Microsoft software has very little ability to handle non-Microsoft Office files.
We would like to apologize for any inconvenience caused.
Certainly, if there is anything else we can do for you, please feel free to inform us.
If you have any questions, please do not hesitate to contact me.
If the answer is helpful, please click "Accept Answer" and kindly upvote it. It will be beneficial to more community members reading here. Your contribution will be highly appreciated.