Documents
Everything in the PDM is a document: a part, an assembly, a code document (a generator), or a drawing or plain document that just holds a file.
A document has a number that's unique in the PDM. Use your own (letters, digits, dot, underscore and dash, like BRK-2001) or let the PDM make one up (DOC-000042). Name and description can change any time. The kind can't.
Where the files are
The database holds the document: its branches, drafts, versions, releases and what it's used in. Each draft and version points at stored files, found by their hash. You see a model and what ClassCAD measured in it, not the files: a part is made in the PDM, opened in Buerligons, saved back into its draft. The files are there, under Files, for the exceptions: a model from another system comes in by Upload, and someone who wants to work on a part offline downloads it, reserves the branch and uploads the result. The kinds of file are listed in Files and jobs.
Folders
Each document lives in one folder, or in none, which the list calls Unfiled. Folder names are unique within their parent. Moving a document isn't a change to it: its versions and its ETag stay as they are, and only the audit log notes the move. A folder can be deleted once it's empty.
Search looks through all folders and shows where each hit lives. A generator files what it makes into a folder of its own, named after the generator and created on its first run.
Archive, delete, copy
A document with a released revision is never deleted. It's archived instead: hidden from the list unless you ask for archived ones, read-only, and back with Unarchive. A document that was never released and isn't used by an assembly can be deleted.
Copy makes an independent document from any draft or version, with a new number and a history of its own. It's also how you take a generated part and keep working on it by hand.