Answered by Mike, Hiring Expert at Avery Dennison Corporation, on Friday, November 2, 2018
Congrats on your offer! That's exciting news, but a challenging situation. Having been on both sides of that situation (employer and candidate), I could definitely relate.
First off, I think you should clarify with the company when they expect you to respond to their offer. While some companies might expect responses in 2-3 days, some are a little more lenient and allow for a week or two. In either case, I think it would be important to clarify early on.
If they are looking for a quick turnaround on your response, it's not inappropriate for you to ask for an extension. While I wouldn't necessarily let them know you are expecting another offer, I would let them know that you need more time to decide. Most companies will be agreeable to that.
There might come a point, though, where you might need to make a decision on either passing on the current offer (in hopes of getting an offer from the second company), or accepting the offer you have received. I know that could be a tough decision, but at some point you might need just make a decision.
Best of luck! Thanks!