
kadance |

From the PRD entry for Intimidate, emphasis mine:
Demoralize: You can use this skill to cause an opponent to become shaken for a number of rounds. The DC of this check is equal to 10 + the target's Hit Dice + the target's Wisdom modifier. If you are successful, the target is shaken for 1 round. This duration increases by 1 round for every 5 by which you beat the DC. You can only threaten an opponent in this way if they are within 30 feet and can clearly see and hear you. Using demoralize on the same creature only extends the duration; it does not create a stronger fear condition.
So, intimidate can't be used twice on the same creature to make them more than shaken, but it still stacks with other fear effects like Frightful Presence.

kadance |

Best I can find is this salient post by
Jun 6, 2013, 02:15 PM | FLAG | LIST | FAQ | REPLY
Well, I went digging a bit. Here's what the offical CRB errata Update 1.2 — Release Date: 08/20/10 says:Quote:
Page 99—In the Intimidate skill, add the following
sentence after the first sentence of the Demoralize paragraph:
"This shaken condition doesn’t stack with other shaken
conditions to make an affected creature frightened."
My fourth printing PDF does not have this language in it, nor does my 5th printing PDF.The 1st to 6th printing errata says "Using demoralize on the same creature only extends the duration; it does not create a stronger fear condition."
So it seems that in 2009, it did stack, then in 2010, it no longer stacked, and now it possibly does. I can't be sure as it's really hard to disprove a negative, and the FAQ has zero to say about it.
Please note, that errata update is no longer pushed out, is not included in the prd, and is not included in the most recent erratas/faqs/printings of the CRB.
In short; if they didn't mean for Intimidate to stack with anything, they would have included this errata or something like it, but they have not for the last 5 years.

wraithstrike |

Best I can find is this salient post byTwoWolves wrote:Jun 6, 2013, 02:15 PM | FLAG | LIST | FAQ | REPLY
Well, I went digging a bit. Here's what the offical CRB errata Update 1.2 — Release Date: 08/20/10 says:Quote:
Page 99—In the Intimidate skill, add the following
sentence after the first sentence of the Demoralize paragraph:
"This shaken condition doesn’t stack with other shaken
conditions to make an affected creature frightened."
My fourth printing PDF does not have this language in it, nor does my 5th printing PDF.The 1st to 6th printing errata says "Using demoralize on the same creature only extends the duration; it does not create a stronger fear condition."
So it seems that in 2009, it did stack, then in 2010, it no longer stacked, and now it possibly does. I can't be sure as it's really hard to disprove a negative, and the FAQ has zero to say about it.
Please note, that errata update is no longer pushed out, is not included in the prd, and is not included in the most recent erratas/faqs/printings of the CRB.
In short; if they didn't mean for Intimidate to stack with anything, they would have included this errata or something like it, but they have not for the last 5 years.
Not updating a rule for years is not a sign of "intention". There are still rules in the CRB that we are waiting for answers on.