Hi, I realize this has been a while, but I too am now having the same problem. The leader lines are fine within the mxd, but will not export (to anything, not pdf, jpg, etc). Did you ever get this resolved? I'm at an absolute loss. Thanks.
I am having the same problem as well. Everything looks good in the mxd, but the pdf version is missing random leaders. No setting adjustments have fixed it.
I send these pdf versions out to multiple users and it's quite embarassing to have them looking so unprofessional.
You wouldn't happen to have the data frame rotated, such that North is no longer straight up, would you? I have seen similar quirks to what you describe when the data frame rotation was set to anything other than 0.
Just a thought. Thanks