This is a paid asset, but now you can download Capture and Save (Lite) Free.
Detail this asset from Unity Store: Original Link
Capture and Save Lite v3.8
“If possible, please buy the package to support the developer”
CaptureAndSave is a great plugin for game developers who want to capture screen and save to Camera roll or Picture folder of the native platform.
Features :
– Capture and save screenshots to your My Picture folder by default on PC and MAC.
– Capture and save screenshots to your camera roll by default on iOS.
– Capture and save screenshots in your specific path on MAC and PC.
– Capture and save screenshots in your Picture folder on Android.
– Capture and save full screenshot
– Capture and save specified screen area.
– Save your texture to gallery/ Camera roll
– Fast Capturing than built-in method
– Gallery refreshed after taking snapshot in android
– Preview before saving to gallery.
Included Files:
– Integration Guide
– Documentation
– Example Scenes
Also see this blog to compare both (Lite & Pro) version of Capture And Save .
Please drop me a email if you have any :
– General query
– Pre order enquiry
– Support request
– Other requests
 – Free Download){kind=link}