You are downloading the Digital Signature XAP file v2.6.0.0 for Windows Phone. Digital Signature is a free 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! Write. You can now download the offline XAP package file to install & try it.
Download Locations for Digital Signature 2.6.0.0 XAP file
Package File
Please Click Here > to retrieve available package files for Digital Signature.
Please be aware that the Digital Signature XAP file you are to download is hosted on the Microsoft Store CDN server. You can read more about Digital Signature or get it on Microsoft Store.
To try 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.