Write on a PDF with the Pen in 4 steps
- 1
Open the Pen Tool
Go to Pen Tool and select your PDF. The toolbar has two buttons, Select and Pen, with Pen active.
- 2
Set the pen
Pick a Color, a Pen width from 0.5 to 24 pt and an Opacity. For handwriting on letter or A4 pages, 1.5 to 2.5 pt reads well.
- 3
Write
Drag to write. Lift between letters or words as you would with a real pen. The stroke snaps into a smooth curve when you release.
- 4
Save PDF
Click Save PDF. The file downloads ending in -pen.pdf.
What the smoothing does
Mice and trackpads report your movement as a series of small jumps, so raw freehand lines often look wobbly. The Pen drops points that are closer than a few screen pixels apart and then draws a smooth curve through the rest. You lose a tiny amount of fine detail and gain flowing loops and clean letters.
If you need marks that follow your hand exactly, such as tiny check marks or dense shading, the unsmoothed Draw tool is the better fit. The two are compared in how to draw on a PDF.
Using a stylus, Apple Pencil or drawing tablet
- The pen responds to mouse, touch and stylus input in the browser. While the Pen is active, the page does not scroll under your finger.
- Pressure and tilt are ignored. Line width comes only from the Pen width setting.
- Palm touches can start a stroke on some tablets. Undo with the toolbar button if a stray mark appears.
- Switch to Select to scroll, pinch-zoom or move a stroke you have already drawn.
Correcting pen strokes
Undo removes strokes one at a time, newest first. To delete one in the middle of your writing, click it with Select and press Delete. Selected strokes can also be recolored, made thicker or scaled with the corner handles. The Eraser page adds a tool that removes every stroke you drag across, if you would rather scrub.
Pen notes vs. typed comments
Handwritten notes are drawn into the page, so everyone sees them and they print. Nobody can search them, though, and they cannot be replied to. For feedback a colleague will act on, typed notes from Add Comments appear in their PDF reader's comment list. For a signature, Draw Signature is built for the job.
Frequently asked questions
Is the pen line pixelated when I zoom in?
No. Each stroke is saved as a vector curve, so it stays sharp at any zoom level and print size.
Can I change the color of a stroke after drawing it?
Yes. Select the stroke and pick a new Color or Pen width. The next strokes will use that style too.
Can I highlight with the pen?
Use a wide pen at low opacity for a hand-drawn look. For neat highlights that snap to the text lines, use Highlight PDF.