Hello,
you can do this with the PDF24 Reader that comes with the PDF24 Creator:
- Open the bank statement in the PDF24 Reader.
- Right-click at the entry you want to mark and choose "Insert stamp". (Alternatively, choose the tool "Stamp" in the toolbar.)
- In "Choose a stamp", select the category "Symbols" and click "Check mark". The check mark is placed on the page.
- Save the file.
The check mark is fairly large at first. With the tool "Edit" you can click it and make it smaller or move it.
Online, the same works in "Edit PDF" (https://tools.pdf24.org/en/edit-pdf): choose "Stamp", pick the check mark under "Symbols" and move it into place.