Classic 'Flatten PDF' question

Question

So I have created a fairly complex fillable form in Acrobat Pro (10.1.8)... I have saved it for use by other users in Adobe Reader. (File>Save As>Reader Extended PDF>Enable Additional Features...)
The users can open file in Adobe Reader just fine, all formulas work, all values display correctly, life is grand.
Now all I want is for the user to save a 'flattened' version of the pdf to their machine, either to print or email at a later date. If the user saves the document from Reader all fields can still be edited on next use. If I use a "lock all field" button like this:
for (var i=0; i<this.numFields; i++) {
    var f = this.getField(this.getNthFieldName(i));
    if (f!=null && f.type!="button")
        f.readonly = true;
When I open the saved, field locked document, I lose all the formatting in my fields. (ie. no $ symbols, or commas in numbers, etc. )
And of course, there is no "print to pdf" option when you try and go that route... which of course, would make life too easy, wouldn't it?
So. Does anyone have a solution for what I can only imagine is a fairly common problem? I've searched high and low to no avail.

Answer 1

I think I am now realizing the problem here. I wasn't real clear on the difference between Reader and Acrobat. I have always referred to them a Adobe Acrobat Pro and Adobe Acrobat Reader. I realize now that the term "Acrobat" refers to what I called Pro and Reader is actually Adobe Reader, not Acrobat Reader.
So my question (or concern) is still, "Why did Adobe design a method of creating a file that could be changed by anyone along the line?" If I create an interactive form, send it to a client, he fills it out and sends it to someone else, they can change the data in the form. Not a very secure system if you ask me. Seems like there should be a way for the person filling out the form to "flatten" it so no one else can change the data.
You mentioned something about a signature. I am not familiar with this function. If you can explain that quickly to me I would appreciate it. If not I will spend some time to figure it out. Although I find the help files in Acrobat very NON intuitive.