Prepare the area for the Pergo flooring. Sweep or vacuum the subfloor in the doorway.
Locate a small plank of Pergo flooring and a small piece of foam underlayment. Place the Pergo plank upside down on the underlayment. Set the two pieces right next to the doorjamb of the doorway.
Trim away the doorjamb and doorway moldings with a dovetail saw. Use the underlayment and Pergo pieces as a guide for the saw. Cut the moldings and doorjambs and then remove the cut pieces with a screwdriver. Clean the area with a vacuum.
Test the cut doorjambs by sliding the Pergo flooring and underlayment under the doorjambs. If the flooring doesn’t fit you may need to trim a bit more from the doorjamb.
Use the manufacturer's directions to install the Pergo flooring in the room. At the doorway, measure the space for each piece of laminate flooring with a measuring tape. Transfer the measurements to the Pergo flooring planks with a pencil. Cut the flooring to size on the table saw.
Slide the doorway flooring in place under the doorjamb. Tap it in place with a rubber mallet and tapping block.