There is a bug in Yosemite that makes characters of the OTF fonts with the higher value of 1000 to print or show in the PDF made by Apple OS smaller. See this link for sample:
I know that default number of UPM is 1000. But I want to make sure that having higher values is completely permitted and legal. Adobe has fonts OTF with higher UPM like Adobe Naskh or Adobe Arabic. May you give some explanations about UPM value please.