Yes. There are no federal laws that prevent employers from editing or making changes to a job advertisement that has been posted. The only thing that may place a limitation is if an employer is placing a job ad on the State Workforce Agency site in compliance with PERM Labor Certification requirements. The regulations associated with this have very specific guidelines on posting and duration. Depending on whether the changes made are material or not, the employer may have to repost the job and start the clock again.