You can edit your notes any time, and delete your notes if you need to. Typically, we recommend that you keep notes in your account for the benefit of those who already bought it, and also potential future buyers.
To edit your material, just follow the steps below:
1) Log in to your StudySoup account.
2) Click on the menu icon at the top-left side of the page.
3) Click on your name to go to your profile.
4) On that page, go to your "My Uploads" section
5) Look for the material you wish to update and simply click on it.
This should lead you to the upload page, where you can remove the file you added before and add a new one. Don't forget to save any changes to make sure your study material updates correctly.
Here's a quick walkthrough: