Smallpdf trial requires credit card even though I only wanted to test it — how can I try tools without entering card details?

You have to add your credit card or PayPal information for Smallpdf's free Pro trial, even if you're just trying out the tools.

They say this is to make sure the user is real and to make it easy to switch from the free plan to the paid plan if you don't stop in time.

You don't have to enter your credit card information to use Smallpdf. Their free plan gives you limited access but doesn't require you to enter your payment information. You can still use many of their basic tools with this plan.

If the "free trial" way is required to get all the features and a card is needed, you could try other PDF tools that offer "no card needed" free tiers.