FireShot is a good and easy tool to help you make screenshots of your webpages, to embed in your documents, user manuals, SOPs etc.

FireShot

Fireshot is a plugin of Firefox browser, which will help you take screenshots of your webpage or website documents, and not only screenshots, but it also provides an enrionment which will let you modify your screenshots, append text in it, write in different font colors for documentation, show directions or arrows to show the text directions etc.
As said on its official website: FireShot is a extension for Firefox and Internet Explorer that captures, edits, annotates, organizes, exports and prints screenshots of your web pages.

FireShot IE

FireShot is also available to be installed in your Internet Explorer, from where you can make your screenshots using IE.

FireShot Download

To download FireShot for Firefox or IE, or to check out more details about FireShot, please have a look at its official website below:
http://screenshot-program.com/fireshot/

Or goto the Mozilla Addons website, to install it on your Firefox directly, by searching it at:
https://addons.mozilla.org/