In Gmail there is no insert/upload image option by default. Let me show you how to enable the option so you can upload and insert an image into the email or insert an image by providing url.
If you don't have installed program for editing PDF documents on your computer, then you can use web application PDFescape which allows you to edit your documents in your browser.
When you want to copy the result of the cell to another cell in Excel, the target displays an invalid references error messag. This error can be avoided by copying cell value into target cell and not the whole formulas.
If you like the Lords of the Rings movie trilogy, then you might also like this Photoshop tutorial, where we will make a dramatically red sky on a random photograph.