This is a paid asset, but now you can download proSreenShot Solution Free.
Detail this asset from Unity Store: Original Link
proSreenShot Solution v1.28 (Latest version)
proScreenShot is a fully customizable solution for making editor or in-game screenshots.
Platforms – Supports all platforms.
Blend Textures – Blend textures on the screenshots (logos, watermarks, frames, etc).
Fully Customizable – Configure within editor or Scripting API.
Ignore Objects – Set a list of objects that you don’t want to go into the screenshot.
Formats – Set custom encodings, file formats, blend types, custom resolution.
Easy Naming and other – Custom names, add data time to file, randomize, add screenshot sound.
Albums – It will automatically make a history of screenshots for you to easy make screenshot albums and manipulate them.
Open source, examples, documentation!
See Documentation for more details.
For more tools and information visit proUnity Tools
Unity 4.6+ & 5.1+ support!
Very easy to use, enjoy!