Is there a way, without buying additional software, to write protect a dwg file so the person I send it to cannot change it? We work with architects sometimes and some have altered our design file and tried to blame an error on us when it was right on our end. Trying to prevent this in the future. Thanks..
No, there is 3rd party software available that will do that, but nothing you can do in cad can't be edited by a skilled user.
Option 0 is to supply wet ink signed and embossed sealed hard copies as the contract documents
Option A is to supply only DWF/PDF to your clients,
Option B is to purchase and use CADLock
Option C is to digitally sign the dwg files before they leave the building - and keep a read-only archive inhouse - while they can still be edited the digital signature is invalidated, so it's quite easy to demonstrate that the edited version is ot what was sent out
Option D is to supply dwg files on CD-R, and keep a copy of the CD-R along with the signed Letter of Transmittal in the project file. FedEx/DHS/UPS signed delivery receipts are a good thing here
For any of these, if your record keeping and document management cpabilites are weak, you're potentially going to end up in trouble.