question regarding familiars and animal companions

a friend informed me you were not allowed both a familiar and an animal companion at the same time by RAW but i cannot find this anywhere.

furthermore, if you can mount your animal companion are there any action economy benefits? or do you still have to command to get actions, though i guess at that point command to move both you and your companion twice isnt bad.

That sounds like a PFS (Pathfinder Society, which is the 'organized play' uh, organization) rule: I know they had a rule like that for the previous edition, but I'm not certain if it was carried over into PF2E.

Mounted companions are extremely limited if they do not have the 'mount' trait. Even if they do, you both share a multiple attack penalty, so you still can't get more than one attack without a MAP.

Source Core Rulebook pg. 214 1.1

You or an ally can ride your animal companion as long as it is at least one size larger than the rider. If it is carrying a rider, the animal companion can use only its land Speed, and it can’t move and Support you on the same turn. However, if your companion has the mount special ability, it’s especially suited for riding and ignores both of these restrictions.

Source Core Rulebook pg. 478 1.1

You and your mount fight as a unit. Consequently, you share a multiple attack penalty. For example, if you Strike and then Command an Animal to have your mount Strike, your mount’s attack takes a –5 multiple attack penalty.

You occupy every square of your mount’s space for the purpose of making your attacks. If you were Medium and on a Large mount, you could attack a creature on one side of your mount, then attack on the opposite side with your next action. If you have a longer reach, the distance depends partly on the size of your mount. On a Medium or smaller mount, use your normal reach. On a Large or Huge mount, you can attack any square adjacent to the mount if you have 5- or 10-foot reach, or any square within 10 feet of the mount (including diagonally) if you have 15-foot reach.

how does one get the mounted trait for their animal companion is my thought

how does one get the mounted trait for their animal companion is my thought

The horse animal companion has it under special.

Martialmasters wrote:

how does one get the mounted trait for their animal companion is my thought

The horse animal companion has it under special.

is that it? i have a player playing a small character (leshy druid) that wants to ride a medium creature.

i guess i could just fudge it and give his companion the mounted trait for the hell of it, but i wanted to know if there were other ways

Dragorine wrote:

Martialmasters wrote:

how does one get the mounted trait for their animal companion is my thought

The horse animal companion has it under special.

is that it? i have a player playing a small character (leshy druid) that wants to ride a medium creature.

i guess i could just fudge it and give his companion the mounted trait for the hell of it, but i wanted to know if there were other ways

There's nothing saying you can't ride another Animal Companion (as long as it's one size category larger than you) but the animal in question can only move. No attack or support while you're riding it. It is the horse AC's reason for existing really.

EDIT
On a side note as it's your game you could rule that your player could use the train animal feat to train an animal companion have the mounted trait.