Take something long (I used a chopstick, but the end of a pencil or even a pair of scissors will also work well), slip it inside, and nudge the seam into a nice smooth edge.

用个长的东西(我用的是筷子，不过铅笔头甚至剪子也都行)，深入里面，将接缝边缘推的光滑美观。

youdao

Most of the text has a very smooth edge and does not appear choppy at all, but that's not the case for the small text at the top and bottom of the page.

大部分文字都有平滑边缘，但页面顶部和底部的小字则保留了锯齿。

youdao

If you do this the inside cover of your paper will be smooth, if you don't there is a chance there will be a line resulting from the edge of the manilla.

如果你做了这一步，封面内侧会比较平整。

youdao

The climbing now was steeper and more difficult, until finally the stream seemed to drop down over the edge of a smooth granite ledge that rose above them and the old man waited at the foot of the ledge for the young man to come up to him.

NPR: Robert Jordan, Hemingway's Bipartisan Hero