Removing the seeds will not necessarily make the pepper less hot.
The heat of a poblano comes from its capsaicin, a membrane in the peppers' pith or ribs. However, when the seeds come in contact with the pith they may become coated in capsaicin which can make them spicy.

To make the pepper less spicy, you will want to remove the seeds and the pith.
Remove the stem, then cut the pepper in half lengthwise. Use a spoon and scrape out the seeds and membrane. The pepper can still be spicy, but a good portion of the heat is stored in those parts.
During this process, avoid touching your eyes to prevent any irritation.

Dried poblano peppers are called ancho chiles.
When growing poblano peppers for anchos, allow the peppers to ripen to a red color before picking them to be dried. Once dried, these anchos are great for grinding into a chili powder and making sauces, moles, and salsas.

Poblano seeds can be harvested from the pepper and saved for another planting season. Remove the stem from a ripe pepper. Then, cut it in half lengthwise. Use a knife to scrape the seeds out of the pith. Spread out the seeds in a well ventilated area and allow them to dry for several days. Store your pepper seeds in a cool dark place to plant another season.