Are you sure you these files were inserted with the "store a reference" option?
What you describe sounds like a physical copy of the file is being inserted into each container field.
Yes. Originally we stored the physical document in the container and changed it to only a link without a thumbnail view of the document to reduce file space. When you right click on the container in browse mode, the only option is to open the linked acrobat document. The following screen shot is the right click menu.
This actually stores a copy of the file as you appear to be using the Insert Object method supported only in windows via OLE (Object linking and embedding.)
If you use Insert File and select the "store a reference" option in the dialog that appears when you select the insert option, you should see that your file size grows much more slowly as you add records and insert additional files.
Note: I've found an article in the Knowledge base that indicates that OLE is on their "to be deprecated" list for future releases of FileMaker so you might want to transitioin away from OLE now be fore getting caught by suprise when upgrading to a newer version of FileMaker some time in the future...