Checkmarks are a useful tool to have when you're faced with multiple empty forms. Here is how you can get the job done right now.
1. Open your MobiPDF file and click the Fill and Sign tab.
2. Select the symbol you want to add to the file.
3. Click where you want to add the checkmark. Use the dragging points to resize and reposition it as you please.
4. Click away from your checkmark to save it as part of your PDF file.