I need to create three forms. One is already in a PDF and the other two will have to be created from blank forms. I need them to all be in one document so when I send them out the person can open one file and see all three forms. Is this possible?
There is an offering from Adobe Professional Services where they combine the forms into a single xdp on the fly then render that. This solution requires you to have a server product called Livecyle Forms.
Unless you want to combine all three into a common design then no.
Date arithmethic is quite simple using FormCalc. You need to use the Date2Num function. This will give you t he number of days that have elapsed since a set point in time (called the epoch). When you have that you can add the number of days that you want then use num2Date to turn that number back into a date. The code woudl look something like this:
// Get the number of days from the epoch for the starting date
var startDays = Date2Num(DateField.rawValue, "YYYY-MM-DD")