There are no level limits for demihumans in the Penderyn Campaign. They may progress just as the human classes do.

MULTICLASSING

      Having more than one class is possible in the campaign, but there are restrictions and drawbacks. Non-humans, who live a great deal longer than humans and begin play at more advanced ages, are more frequently multi-classed, however, humans may also take on another class after they've adventured a bit in their original class.

     In all honesty, picking up a second class in its entirety is not always an efficient practice, though. Read the guidelines below before deciding to multiclass your PC.

     The upside to multiclassing is that your PC receives all of the class abilities and skills of every class they pursue. Multiclass PCs always use the most beneficial starting proficiency slots, proficiency improvement points, Saving Throws, Hit Points, and combat modifiers from among all their classes.

     The downside is that it's expensive in XP cost. Multiclassers need to gain all the XP in all their classes to move up in levels. All earned XP is divided equally amongst your classes. (So a PC with three classes would take about three times as long to move up in levels as a single-class cohort.)

     PCs who start as multiclassed roll their starting age normally, but then advance one age category (your age becomes the minimum age for the next highest category.)

     Also, there must be a reasonable explanation for your class choices in the campaign. A fifth level fighter who's never once shown a single religious inclination, but suddenly wants his fighter to take a level as a cleric, would have trouble getting the DM's okay, for example.

The DM's Suggestion

     Honestly, if you don't necessarily want every skill that a class has, it's much more effective to pay Proficiency Points and train in a single class skill. In other words, if your ranger just wants to pick locks, but doesn't want to become a full-classed thief, then spend the Proficiency points and get the Pick Locks skill, instead of spending mucho XP to dual-class as a ranger/thief.