What is the requirement?
Do you want the pop-up/dialog box to open for allowing user to sign the signature field or the dialog box of signature validation?
If you add a signature field in LiveCycle Designer then save this file as PDF.
If a user clicks this signature field using Acrobat/Reader then a dialog automatically shows up to select credential and to enter password.
Do you want any other behavior?
I can check how to invoke pop-up when a button is clicked but just interested to know why the user cannot click on signature field directly instead of clicking the button?
Would the signature field be an invisible one?
We are migrarting Adobe 5 forms to Adobe 11. The Adobe 5 forms have a button called "Sign" for capturing the signature. So we want to have the same button her in Adobe 11 too, as we donnot want to disturb the design.