The File Picker Control lets you pick a file and store it's path into an ACT Character Field.  Clicking the elipses(...) button in the control will bring forward a open file dialog to choose the file.

ACTAskToLink
When set to true a window will ask if the file should be linked.  If the answer is yes the file will also be attached to the parent contact, company, group or opportunity as a LNK file.

See also