You are downloading the Digital Signature XAP file v220.127.116.11 for Windows Phone. Digital Signature is a free and useful Business app: *Updated for Windows Phone 8* No longer do you need paper and a scanner, because Digital Signature lets you sign your name on your Windows Phone! ... You can now download the offline XAP file to install & try it.
Download Locations for Digital Signature 18.104.22.168 XAP file
Note: To install it manually from an SD card, you should choose one of the server location above to get the offline Digital Signature XAP file, move the file to your phone's SD card and then tap 'Install local apps' in the phone's App list.