Short answer
It depends on your plan:
Pay-Per-Lead: 1 connected Upwork account.
Unlimited: up to 3 connected Upwork accounts.
Need more than that on Unlimited? Message us in the chat — we can raise your limit.
Managing your accounts
You'll find your accounts and how many seats you've used on the Connected Accounts page. Each campaign bids from one connected account, which you pick in the campaign's Configuration tab.
On older (legacy) plans your limit may be set individually — your Connected Accounts page always shows your current allowance.