Final answer:
To add multiple checkboxes in a PDF, use PDF editing software like Adobe Acrobat, find the 'Prepare Form' option, select the checkbox tool, and place the checkboxes in desired locations in the document.
Step-by-step explanation:
To add multiple checkboxes to a PDF document, you generally need to use a PDF editing software like Adobe Acrobat. First, open the PDF file in the software. Look for the Tools menu or a similar section. Within that, you should find an option to Prepare Form or another variant that allows form editing.
Click on it, and then select the checkbox tool. Click on the document where you want the first checkbox to appear.
You can then copy and paste this checkbox to create multiples or manually add more by clicking again elsewhere on the document. Once all checkboxes are placed, you can save the document with the changes.