I would suggest to write an AEM forms validation expression in Javascript. 

radzmar wrote... Sorry, but this.value != "" isn't a good validation (see here on page 18). You better use this.rawValue !== null; or the built-in method isNull() to check a fields value against null.  this.isNull();    Thanks. I updated the answer !

You can make your filed mandatory to avoid JS. OrYou can write your validation script under "Validate" expression. If you are using rule editor its quite simple. One sample validation is - this.value !==null   or this.isNull() for blank fields. Just write this script in validate expression. 

Thanks for your reply. I am not using JQuery plugin. Is there any way from AEM out of the box ?

I dont think we are looking for this solution. We know that PDF can be sent by AEM Form out of the box. Our case is a bit different" Example, a form has 3 fields.  Upon submit, PDF#1 is generated with all 3 fields and PDF#2 is generated with only fields #2+3.  PDF#1 is sent to email address #1 and P...

Thanks for your reply. We are using Adaptive forms in AEM 6.1