Those that know cannot say. Those that say cannot know.
Right now, Adobe Reader is not available on iOS but there are some third-party PDF reading apps - however their support for things other than simply reading the file tends to be very poor indeed, so forms, signatures, scripting, etc. are going to cause trouble, and the more complex a form is, the less likely it is to run in non-Adobe software.
Meanwhile, it's worth looking at a web-based solution for your iOS users, such as Adobe FormsCentral - as this is rendered entirely in HTML it works on any device. Though it of course requires the user to be online while they're completing the form, with iOS devices that's a fair assumption.
The features FormsCentral supports are constantly expanding, so if there's something you need which isn't available right away, it'll probably appear very soon, and please send in suggestions. You can still use a PDF form for your desktop and offline audiences, and combine the returned datasets using the respective export features of both Acrobat and FormsCentral. Running this two-tier PDF+HTML workflow is getting quite common, as it leaves pretty much every platform and OS avenue open to users, while keeping it quite simple for the form creator to aggregate all the data into a single spreadsheet. PDF forms can be more powerful of course, but until you can open them on your Internet Refrigerator there's going to be a need for a plan B!