¿Como agregar Firmas automatica en hojas pares?

It looks like you using the "Sign Yourself" tool. This tool places a flattened image of your hand writen signature onto the PDF. 

Automating this process is doable, but requires some effort.  First of course is that you'll need an image of your signature. The one that Acrobat is using is not available to the scripting model. Then you'll  need an automation script to apply the images.  For this to work you'll need to know the target locations for the signatures on each page.  The simplest scenario is if the location is exactly the same. But if not, then the next best scenario is that the location is marked by some unique text that can be found by the script.  Otherwise it gets more complicated. 

There is another option, which is to shortcut the manual process by removing a mouse click. Turn your signature image into a stamp. The stamp tool can be "pinned", or turned on continously so that every click places a stamp. 

This is a common mistake people make regarding digital signatures. There's absolutely no need to sign multiple pages using the same signature. A digital signature applies to the entire file as a whole, not just to the page it appears on. In fact, it doesn't need to appear on any page(s) at all, and can be totally invisible, and still be valid.

If someone else is requiring you to sign those pages use something like a stamp or even an image, and then sign it once.