Update (19-04-2014): Another new feature! It's now possible to specify the dimensions of the blank page(s) you're adding with a simple dialog that appears when you select where to add them.

The dialog allows you to enter the desired width and height of the page, in either Inches, Millimeters, or PostScript Points.

Update (17-10-2014): I just added a brand new and powerful feature to this tool! You can now insert multiple blank pages after every X amount of pages into your file. So not just a single page as before, now you can insert many pages in seconds.

With this script you can insert a new blank page to you PDF files with a single click! The size of the pages will match the size of the other pages in your files.
You can choose from the following options:

• Insert a blank page at the beginning of the file
• Insert a blank page at the end of the file
• Insert a blank page before the current page
• Insert a blank page after the current page
• Insert a blank page after/before every X pages

When installed, the tool adds a menu button to Acrobat with these options:

If you select the last option you're presented with this dialog where you can define how and where to insert the blank page(s) you want to add to the file:

The results can be seen in the Pages panel on the left:

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