Two handy workflows I have in my PDF Services folder in the main Library on my Mac failed, allegedly damaged or incomplete. One was Create Booklet, the other was compress PDF. Neither workflow were actually damaged or incomplete, Sierra just went on strike & refused to work with them, so I had to recreate them from scratch. The Booklet item I had added in the past from a free download, now it's a $15 download from the MAS. I wasn't going down that route so I internet-hunted until I found a copy of the original & installed it.
Compress PDF used to be an Automator action but it's now been removed. I had to use the "Compress Images in PDF" action, selecting jpeg & medium level compression. When tested, a 4.8 MB PDF dropped to 650 KB with no noticeable loss of quality.