The 4.5.3 version of Scriptation for Mac was available to download on the developer's website when we last checked. We cannot confirm if there is a free download of this app available. This free Mac app was originally designed by Scriptation LLC. We recommend checking the downloaded files with any free antivirus. The software lies within Productivity Tools, more precisely Office Tools.
From the developer:
Scriptation is the PDF annotation app for the film, television, and video industry. It is a revolutionary app for production that intelligently transfers your annotations, notes, and markups into new script revisions. Whether you're a filmmaker on a big budget feature or a student on your first production, Scriptation makes it easy to go paperless, increase your productivity, and save hours of time.
You may want to check out more software for Mac, such as PDFMergeThing, NanoCount or okular, which might be similar to Scriptation.