Drawboard PDF does not auto save your documents. Rather, it keeps a temporary 'scratch' file of your unsaved annotations in a file, waiting for you to save. This should not be relied upon as a manner of saving your files.
Drawboard PDF currently stores your temporary file data in the following directories:
^clicking your address bar in your file explorer will usually reveal your username.
WARNING: Moving files from these directories may cause saving and file opening issues in the app. Copy and paste them elsewhere first instead of opening them up directly.