Stay at the Nines, if your business allows you to choose your hotel. It's a very cool place.
Walk around the Pearl District and be sure to make time (lots of time!) for Powell's bookstore. If you love books, it is not to be missed. Walk around Alberta Arts District. Ice cream at Salt & Straw. Eat at The Waiting Room in the Alphabet District. You won't be disappointed. Portland City Grill is a great restaurant with lovely views of the city.
The International Rose Test Garden is beautiful, but bloom season is over now. Put that on your list for your next visit.
Enjoy your trip! Portland is a very fun city to walk around and people watch. Just be mindful of your surroundings, since it will be dark by the time you're able to get out and do things. Would not walk near the river by yourself. I walked aournd the Pearl District by myself at night when there were lots of other people out dining and shopping and was fine.