Summarize the following:
The best option is type the addresses. You can either use labels that you print on or print directly on the envelope. You can also just print on a plain piece of paper, cut the label out, and glue it on, though that can end up being messier.  Your word processing software should have templates for printing on both labels and envelopes. Pick the template that matches the labels you bought, then type out the address for both the sending address and return address. Alternatively, pick the template that matches your envelope, then type in the addresses and print it. When mailing a letter such as a resume, think about using a 12 by 9 envelope. That way, you don't have to fold your letter to fit in the envelope. When the recipient gets it, it will look more professional. Keep in mind, though, that larger envelopes cost more to mail. Keeping it uncreased also allows the employer to make copies more easily. Paperclips and staples can make the resume look less professional. A better option is to use neither, and just make sure you have your last name and a page number on each page, so if one gets mixed up with other papers, it can be placed back in order. Some people use mailing services to send out large numbers of their resumes to potential employers. However, many of these companies use the same fonts and styles for all their resumes, and employers will reject them without even looking at them. Stick to doing it yourself.

Summary:
Type the addresses. Consider using a full-sized envelope. Avoid using paperclips or staples. Skip mailing services for resumes.