docs: rewrite agent-pdf README with usage details, privacy, and limits

Author: bendersej

agents/README.md

@@ -1,6 +1,8 @@
 # agent-pdf
 
-Let AI agents edit and fill PDFs through [SimplePDF](https://simplepdf.com).
+Give any AI agent the ability to edit and fill PDFs. No API key, no server-side processing, free.
+
+Powered by [SimplePDF](https://simplepdf.com). [Source code](https://github.com/SimplePDF/simplepdf-embed/tree/main/agents).
 
 ## Add the [edit-pdf SKILL](https://agents.simplepdf.com/SKILL.md)
 
@@ -26,7 +28,7 @@ curl "https://agents.simplepdf.com?url=https://example.com/form.pdf"
 curl -X POST https://agents.simplepdf.com -F file=@document.pdf
 ```
 
-Returns:
+Returns a ready-to-use editor link:
 
 ```json
 {
@@ -36,6 +38,31 @@ Returns:
 }
 ```
 
-## Source code
+The user opens the `url`, edits the PDF in-browser, and downloads the result. All client-side.
+
+## Connect your SimplePDF account
+
+Free to use as-is. Connect a [SimplePDF](https://simplepdf.com) account to add branding, webhooks, and storage:
+
+```bash
+curl "https://agents.simplepdf.com?url=https://example.com/form.pdf&companyIdentifier=acme"
+```
+
+With a `companyIdentifier`, you get:
+
+- **Custom branding**: match the editor to your product ([guide](https://simplepdf.com/help/how-to/customize-the-pdf-editor-and-add-branding))
+- **Email & webhook notifications**: receive submissions in your backend ([guide](https://simplepdf.com/help/how-to/configure-webhooks-pdf-form-submissions))
+- **Bring Your Own Storage**: route PDFs to your S3 or Azure bucket ([guide](https://simplepdf.com/help/how-to/use-your-own-s3-bucket-storage-for-pdf-form-submissions))
+
+## Privacy
+
+- **URL input**: passed directly to the browser editor, never downloaded or stored by this service
+- **File upload**: stored for up to 24 hours, then automatically deleted
+- **Editing**: entirely client-side, edited documents never touch SimplePDF servers
+
+## Limits
 
-[github.com/SimplePDF/simplepdf-embed/tree/main/agents](https://github.com/SimplePDF/simplepdf-embed/tree/main/agents)
+- Max PDF size: 50 MB (file uploads)
+- Uploaded files expire after 24 hours
+- Rate limit: 30 req/min per IP
+- URLs must start with `https://`