Master PDF Editor
Handles interactive forms (checkboxes, text fields) very well.
Also allows you to directly edit the PDF content (text, images).
Limited free version: some advanced features are locked.
Useful if you want a comprehensive tool, similar to Adobe Acrobat.
Foxit Reader
Compatible with PDF forms, checkboxes, and signatures.
Modern and fast interface.
Proprietary software, not always available in official repositories.
A good choice if you want a lightweight but reliable form reader.
LibreOffice Draw
Can open a PDF and let you edit or add elements.
You can export a new PDF with your changes.
Not optimized for interactive forms: checkboxes are not always recognized.
Useful for editing or correcting an existing PDF, but not ideal for form tracking.
Summary:
Okular remains the most reliable for interactive forms.
Xournal++ is perfect for advanced annotation.
Master PDF Editor or Foxit Reader are suitable if you want an alternative closer to Adobe Acrobat.
LibreOffice Draw is useful for editing PDF content, but not for checking boxes.