It all depends on what you want to do. The most convenient way for a PDF for to talk to a server is through the doc.submitForm() function. The SOAP object doesn't work with Reader.
Read this article: http://acrobatusers.com/tutorials/form-submit-e-mail-demystified
Write your scripts in any server side scripting language, ASP.NET, PERL, Java, PHP, etc.
The form submit and SOAP are both for communicating between Acrobat and a server. Manipulating a PDF server side is a completely different game. You'll need a PDF Library. Fortunately there are several to choose from, iText, QuickPDF, ASPPDF. Just do a search.
What is it that you want to do?
Thom Parker
The source for PDF Scripting Info pdfscripting.com
The Acrobat JavaScript Reference, Use it Early and Often
The most important JavaScript Development tool in Acrobat
The Console Window (Video tutorial)
The Console Window(article)
Having trouble, Why Doesn't my Script Work