Detailed steps:

1. First, open pr, then import the required material file and finish editing.

2. Then click the Export command under the File tab.

3. Select the export media option here.

4. In the Settings panel, after selecting the exported encoding format, change the preset to Custom.

5. Then remove the check mark to the right of the resolution to make the resolution adjustable.

6. In this way, you can modify the resolution of the exported video, and you can see that the original video will have a border after the resolution is improved.