Whether an action creates merits or karma depends on your motivation. For a action to create merits, the motivation from the side of the subject must be free of the eight worldly concerns (gain and loss, comfort and discomfort, praise and blame, fame and bad reputation). Actions that are not free from the eight worldly concerns will only create karma that will be used up once the karma is ripened and the effect is experienced. Merits created will not be exhausted until we reached full enlightenment.
The recipient of the action is done to does have an effect on the merits or karma created. For eg more merit and good karma (depending on your motivation) will be created if we give to the Buddha, Dharma and Sangha, people in great need, people who are kind to us or people with higher attainments than us.
However, whatever our motivation may be, any action done in relation to a enlightened object will create an imprint of enlightenment in your mindstream and this imprint will follow you from life to life until you encounter an object that triggers the opening up of the imprint. For eg, if you have an imprint of enlightenment in your mind and when see a picture of a monk, your imprint may open up and you may start to get interested in Dharma, find a guru and practice. In this instance, the merit you have created in the past will be a catalyst to open up your imprints.
To answer DD's question, in relation to people who pick up DS brochures, recite the mantra, or make offerings in front of a DS image they have printed from the website, whether merit or karma is created will depend on whether they are motivated by the eight worldly concerns. However, as DD has mentioned below, they are definitely creating the imprints of enlightenment for future lives.