Uploading your own PDF is super simple.
On the dashboad, you can drop your PDF from your file manager right into this box.
Alternatively, if you click on that box, you can then find and upload your PDF in your file manager.
You'll then see this page, which allows you to enter in a title for the document (one is autogenerated), and description. This is useful in case you need to locate the document later.
If you need to change documents, refresh the page, and you can start again.
Click upload, and your document is ready for sending and signing.