Reasons for change might be important to the employer at the interview, but they are not relevant at this point. Use this precious space to sell, not to justify. To employers this is a given. If you aren't prepared to produce them on demand, you simply won't get the job. Type all letters.
Employers type even personal notes, so follow suit.
Never photocopy a letter-each must be an original. Make paragraphs approximately the same length. Always send a letter with a r sum , never a r sum alone. Check your work carefully for grammar and spelling. It is a good idea to have someone else proofread it.