Check how to add a check mark in a PDF with Adobe Acrobat Reader on Mac and Windows. Step 1: Drag and drop your PDF file into the software to open it; Step 2: Click Fill & Sign in the right tools pane; Step 3: Choose the tick mark on the top pop-up bar, and click into a checkbox to add a checkmark;

Open the PDF. Click "Comment" (upper right of Reader). Click "Annotations" to display the Annotations tools. (the Stamp tool lives here) Click the Stamp tool (top row - far right icon - the shape ids it). Click "Sign Here" and select the check mark.