If an online application only asks for you to upload your resume, is it bad to put your resume and cover letter on the same pdf file?

There's no area to submit anything extra, like a cover letter. I thought that I could put my cover letter in the same pdf file as my resume (ie. Save both as one file), and submit it that way.

Initially, I thought that it wouldn't be a big deal, but I don't want to come off as someone who doesn't know how to listen to instructions or prompts. What is better?

usa jobs
usa jobs resume
usa hotel jobs
usajobs
usa jobs federal government
usa job in ksa
usa jobs
usa jobs login
usa jobs gov
usajobs.gov
www.usajobs.gov
usajobs.com
usajobs
usajobs.gov official