Securing your resource is probably the number one thing you need to think about. It can't be stressed enough that you have to make your work flat/secure before you offer it in your shop.
This is even more important if you are using someone else's resources such as clipart, borders, background images, etc. They have specifically included a TOU that states their work needs to be secure and that if it's part of a resource, the buyer cannot pull pieces of it out to use independently. No one should be able to copy and paste the clipart and use it in another document.
If you are creating in Adobe Illustrator, you can save your project as a PDF and set the securities before you finalize the save:
That blue hightlighted box that reads "Enable copying of text, images, and other content" needs to be UNMARKED!! You don't want to make it possible for them to copy your work or supplies. The drop down that says "Changes Allowed:" should be marked "insert, delete, or rotate". I usually mark this so a buyer can print the pages they want or change the orientation of a page to fit what they are printing on. It can also be set to none.
The same settings can be applied in Adobe Acrobat Pro:
The settings are identical in both programs. The only thing that is different is the color of the background!
Check, double check, and then check again. There are serious fines associated with not following an artists TOU and that is the last thing your little shop needs!