I want a field in Adobe acrobat in which when i click once it show "+", when twice it show "-" and when click thrice blank

Here, I wrote for you a code that will allow you to cycle through a list of any number of characters. You need to place it as the MouseUp event of your button field (and set the caption to the first item in the list):

var values = ["+", "-", "/", "*", "?", "!"]; // etc.
var currentSymbolIndex = values.indexOf(event.target.buttonGetCaption());
if (currentSymbolIndex==values.length-1)
    event.target.buttonSetCaption(values[0]);
else event.target.buttonSetCaption(values[currentSymbolIndex+1]);

You can put that code in a function as a doc-level script and then just call it from each one of your fields. That way you can update the list in a single location and it will apply to all of them.