Adding respondents after your poll is completed widens your sample size. This is a better option than re-running the same poll separately. By using the Add more respondents function, you're guaranteed to get different respondents than the ones you already polled.
To add responses, click the +Add more respondents button near the top right of your poll results.
On the next screen, you'll see a drop-down to increase your respondents. This drop-down will show the price of the addition according to plan tier (Free Forever, Starter, Professional, Business, or Enterprise).
Choose the option you want, and complete checkout by clicking on the Complete Order button.
Note: You can extend a PickFu poll within 120 days of completion; after that, you no longer have the option to add more respondents.