No, compressing the TIFFs to another format before using Acrobat Pro won't improve your compression. PDF uses several different compression methods, including JPEG and the superior JPEG2000, so it's actually better if you haven't used a lossy compression format before sending it to Acrobat. JPEG is also a poor format for Scan Tailor text compression, because it's pure black and white. Acrobat will select a better compression automatically.
If your TIFFs have both illustrations and text on the same page, you'll get the best compression by using a script that can separate layers like Strider1551's djvubind
for DjVu, or my own PDF maker script that I'll be releasing in the near future.
The opinions expressed in this post are my own and do not necessarily represent those of the Canadian Museum for Human Rights.