I am trying to figure out if this is the correct solution.

Out db is living on and served from FMPSA 9 on a mac.

I want to reletively link pdfs to a container field. All the pdfs live on a separate server. These pdfs are not in a web folder and are maintained and updated by ten different designers.

This is working just fine right now in testing using FMPA 9 client. When a pdf is updated, it is also updated at the client level. When I try to use IWP the content of the container is not viewable because it is not in the server web folder. We do not want to maintain two sets of files and moving our fileserver onto the webserver is not an option.

Will supercontainer solve these problems?

SuperContainer will work very well for storing your PDF documents and allowing your IWP users to view them without putting them in your web server folder.

However, it is not recommended that you access SuperContainer documents through the filesystem. It is ok to save over documents like your designers are doing, but adding and deleting directories and files can cause problems matching the directory names with FileMaker. Your developers may be used to dealing with this already if they are working on documents being referenced in filemaker. Changing the filename of a document being referenced will break a container reference. With SuperContainer, the filename doesn't matter, but you do need to have a specific folder structure with each file in its own folder. This sounds strange, but actually works very, very well when using SuperContainer with FileMaker.

I think that you will find SuperContainer to be a very good solution for what you are trying to do, as long as your people working on the files outside of FileMaker understand what can and cannot be changed (don't change directories, one file per folder). You can download a demo of SuperContainer from http://360works.com/supercontainer/ and give it a try.