This contribution unveils and defines the concept of covalent printing onto cellulose paper through the support of a simple and efficient strategy. A photoresponsive cellulose paper bearing disulfide functional groups was created as a molecular printboard for spatio-temporal writing through thiol–X ligation of functional inks upon light irradiation. This strategy using molecular inks in a modular way culminated with the creation of patterns with a high resolution. Hidden covalent writing to the naked eyes was developed through the use of coumarin-based inks while the use of colored inks containing a rhodamine backbone established an uncovered pH-responsive covalent printing, both strategies can potentially find applications in the formation of anti-counterfeiting devices.