Helpful information about DDFs and the "Always use Document DDF" preference
DesignMerge stores the settings for each of your DDFs in your user preferences on a computer, and additionally stores inside a document a copy of the DDF's settings that were last used on that document. Each time you save a document after assigning or editing a DDF, DesignMerge replaces the copy of the DDF that was stored inside that document with a new copy of the selected DDF.
DesignMerge always uses the DDF's settings that are stored in your user preferences on your computer. The "Always Use Document DDF" preference allows you to automatically update the settings of a DDF that is stored in your user preferences with the DDF's settings that have been stored in a document. By default, this preference is not enabled (unchecked).
When this preference is not enabled (unchecked), then DesignMerge always uses the version of the DDF that is stored inside your user preferences on your system. Therefore, if a DDF that is stored inside a document has the same name as a DDF that is stored in your user preferences, the version of the DDF that is stored in your user preferences is the one that will be applied to the document. Additionally, if you reselect or edit this DDF that is stored in your user preferences while this document is open and then save the document, then the previous version of the DDF that was stored inside the document will be replaced by the version of the DDF that is in your user preferences.
When this preference is enabled (checked), the version of a DDF that is stored inside a document will automatically replace the version of a DDF that is stored inside your user preferences. This happens immediately when you open the document. There is no warning or prompt when this happens. You can still edit the DDF, however you cannot select a different DDF until you turn this preference off.
For more information, see the new "DesignMerge Database Definitions" manual, now available in PDF format in DesignMerge Documentation. To download the latest version of DesignMerge Documentation, go to http://www.designmerge.com/documentation.