There are no direct ferries that connect Losinj island and Pag island, although the distance between these two islands is 32 km only.
Here are your best option for traveling by bicycle:
Step 1: Get on the ferry from Mali Losinj to Zadar https://www.croatiaferries.com/malilosinj-zadar-ferry.htm – book this ticket well in advance as you also have to book a place for your bike and the number of bikes on board is limited.
Step 2: From Zadar get on your bike and ride to Pag Bridge (it is only a 29 km distance), cross the bridge and you are already on Pag island.
The alternative is to get your bike on the bus from Zadar to Pag with the Arriva bus company (1-hour bus ride). They take bikes on board if “ there is the sufficient load carrying capacity, what has to be checked at boarding. The fee for the transport of bicycles is paid according to the valid price list” (copied from their FAQ page)
Basically, what they said is they will take your bike on board if there is enough space available. So, get to the bus station well in advance to make sure you are first in line.
Check also this topic: https://www.croatiaferries.com/topic/ferry-from-losinj-to-pag/
