Yes - you can mark up PDFs with this eReader and add handwritten notes, especially with the Kobo Stylus 2; however, full PDF editing (e.g. re-setting text or exporting complete edited PDF files) is limited.

Context and details:
- Display and navigation: The reader displays PDFs in portrait and landscape format, allows zooming/zooming and panning of the section as well as scrolling using buttons or touch gestures.
- Notes and markers: You can use the Kobo Stylus 2 to create handwritten notes, set coloured markers and also write sketches, diagrams or equations in the extended notebook.
- Limitations: The device is primarily a reader; functions such as deep PDF editing (e.g. text editing within a PDF, reliably attaching markers to OCR text or exporting a fully edited PDF) are not available to the same extent as desktop PDF editors and have been described as limited in tests/forums.
- Import/export: Documents can be imported and synchronised via cloud services; exporting/sharing notes or edited PDFs can be limited in some cases and depends on the note mode used.

If you mainly need to annotate, highlight and take handwritten notes, the device fulfils these tasks well. If, on the other hand, you expect a complete PDF editorial team (editing text, extensive page layout changes or reliable PDF export with all annotations), a desktop or tablet PDF editor is more suitable.