Can I write on printed Custom Letterhead with a pen?

Yes, as long as you print on uncoated paper. Uncoated stock has an open, slightly porous surface that absorbs ink from ballpoint, gel, and rollerball pens without beading or smudging. Coated stocks (gloss or matte film) seal the surface, so pen ink sits on top and can smear or take a long time to dry. For letterhead you plan to sign or annotate by hand, uncoated is the safe choice.

• Uncoated text or bond: accepts pen, pencil, and desktop-printer toner cleanly, best for signatures and handwritten notes.
• Gloss or matte coated: vivid color and photo detail, but pen ink can bead up or smudge.
• Laser and inkjet: both run through uncoated letterhead without trouble, so you can print your body copy at your desk.
• If you want a coated look and a writable area, print the letterhead uncoated and reserve gloss for pieces that are not handwritten on.