The Edit Menu lets you copy and paste text. It also lets you find and replace text as needed. If you want to copy text from one page to another, you can do so by doing one of the following

Edit Cut 

or 

Edit Copy 

.

Once you open the new page, you can paste the copied text by doing the following

Edit Paste

This will copy the text in the appropriate place

If you want to select everything on a page you can use the following option

Edit Select All

This will look something like this

The edit menu lets you find text in a page to. In addition you can also replace text.

Lets say you want to find the word LEFT JOIN in the document. Try the following

Edit  Find

Type in LEFT JOIN

Now lets say we want to replace LEFT JOIN with RIGHT JOIN, you can do the following

File Replace

Enter LEFT JOIN in the top one

Enter RIGHT JOIN in the lower one

and click Replace