Documentation: Add Password Removal workflow action documentation (#13377)

Addresses discussion #13373. Documents that password removal creates a
new document version via re-consumption of the decrypted file rather
than editing in place, and explains why the Consumption Started trigger
produces an initial un-OCR'd version followed by a properly processed
one.

docs/usage.md

@@ -620,6 +620,34 @@ no other workflow will be executed on the document.
 If a "Move to Trash" action is executed in a consume pipeline, the consumption
 will be aborted and the file will be deleted.
 
+##### Password Removal {#workflow-action-password-removal}
+
+"Password Removal" actions attempt to remove password protection from encrypted PDF documents. You can specify:
+
+- One or more passwords to try, separated by commas or new lines
+- Each password is tried in order until one successfully unlocks the document
+
+Password removal never modifies a file in place. Instead, once a working password is found, the
+decrypted content is consumed as a new [document version](#document-file-versions), leaving the
+original (still encrypted) version in the document's version history.
+
+**Consumption Started**: because this trigger fires before the document exists yet, the password
+removal itself is deferred until after the initial consumption of the encrypted file has completed.
+OCR engines cannot process an encrypted PDF, so this first version is typically stored with no
+extracted text (unless the file already contained extractable text outside of OCR). Immediately
+afterwards, the password is removed and the decrypted file is automatically re-consumed as a second,
+new version of the same document, this time with normal OCR/text extraction applied. In other words,
+a password-protected file added with this trigger will briefly exist as an un-OCR'd version before
+the properly processed version is created.
+
+**Document Added**, **Document Updated**, **Scheduled**: these triggers run against a document that
+already exists, so password removal happens immediately: the decrypted content is queued for
+consumption as a new version right away. Note that if the document's initial consumption also
+happened while it was still encrypted, that original version will likewise be missing OCR text.
+
+**Current limitation**: Passwords are stored as a simple list without descriptions. To handle
+multiple PDF types with different passwords, create separate workflows for each use case.
+
 #### Workflow placeholders
 
 Titles and webhook payloads can be generated by workflows using [Jinja templates](https://jinja.palletsprojects.com/en/3.1.x/templates/).