Here are the typical editing symbols used by most publishers:

Here are some lesser known editing symbols, curtesy of Brian A. Klems: 

H/t Writer's Digest.

All 8,000 of Maryland's Prince George’s County Public Schools' high school diplomas contained a spelling error which was not caught until graduating students called attention to it. The diplomas spelled the word "program" as "progam".

Surely, with 8,000 diplomas being distributed, some teacher, principal, or even school janitor should have noticed the mistake. However, none did, and at least one principal was still unaware of the error until asked about it by reporters. 

While the typo probably originated in the school district's office, and the school district had to have signed off on the diplomas before they were printed, the printing company is taking the blame and is reissuing the diplomas at a cost of over $20,000. 

This was an expensive mistake.

Details can be found here.

According to the Mail, a publishing house decided to take the free Amazon Kindle edition of War and Peace and market it under their imprint for the Barnes and Noble Nook. Of course, the version from Amazon clearly stated that it was produced for the Kindle, so the publishing house wanted to remove the word "Kindle" from their edition and replace it with "Nook". All they needed to do was find and replace. Or, so they thought. 

Unfortunately, War and Peace was written in the days before electricity, which meant that many fires had to be kindled in order to provide heat and cook food. Hearts can be kindled as well. And, the Victorian-era translator of Tolstoy's work was adept at using the word "kindle" in many other metaphorical ways. 

Here are just a few of the results of their misguided effort to find and replace "Kindle" with "Nook":
  

• 'When the flame of the sulphur splinters Nookd by the timber burned up, first blue and then red, Shcherbinin lit the tallow candle...'
• 'Captain Tushin, having given orders to his company, sent a soldier to find a dressing station or a doctor for the cadet, and sat down by a bonfire the soldiers had nookd on the road.
• 'Believe me,' said Prince Dolgorukov, addressing Bagration, 'it is nothing but a trick! He has retreated and ordered the rearguard to nook fires and make a noise to deceive us.'
• 'Fly to a brother's aid whoever he may be, exhort him who goeth astray, raise him that falleth, never bear malice or enmity toward thy brother. Be kindly and courteous. Nook in all hearts the flame of virtue. Share thy happiness with thy neighbor, and may envy never dim the purity of that bliss.'
• 'It was as if a light had been nookd in a carved and painted lantern and the intricate, skillful, artistic work on its sides, that previously seemed dark, coarse, and meaningless, was suddenly shown up in unexpected and striking beauty.'

(As collected by the Mail.)

One big reason why the editing profession is in decline these days is that people do not really understand what editors do. They think editors can be replaced with spell check and with mechanical tricks such as cut and paste, and find and replace. At a bare minimum, an editor is someone who reads a manuscript to make sure that it makes sense and serves the reader in the best way possible. The features of MS Word or a publishing software program are simply no replacement for someone reading a manuscript with understanding to make sure that it is correct.