How do I easily delete characters in a TextEdit document which I did not type? I have typed a 2 page document using Apple's TextEdit on a Mid 2007 iMac running OS X Yosemite 10.10.5. After closing in RTF format and later reopening, I saw many characters (backslashes, etc.) that I didn't type in. 

How do I correct that easily (Help section didn't help)?
It sounds like you perhaps opened the doc as plain text instead of rtf.  I think you can set it to open as rtf in the Text Edit Preferences.