1. Open WPPDF, and then open the document to bookmark.

2. In the toolbar, click the Bookmarks button (usually a bookmark icon).

3. In the "Bookmarks" window that pops up, you can see all existing bookmarks. Click the Add Bookmark button (usually the plus icon) to add a new bookmark.

4. In the pop-up window, enter the name of the bookmark, and then select the page to bookmark. You can select a page by clicking the page thumbnail in the page list or entering the page number in the input box below the page list.

5. Click "OK" button to add bookmarks.

6. In the Bookmarks window, you can see the newly added bookmark. Click the bookmark name to jump to the page where the bookmark is located.

7. If you want to delete a bookmark, just select the bookmark in the bookmark window and click the Delete button (usually the trash can icon).

8. If you want to adjust the order of bookmarks, just select the bookmarks in the bookmarks window, and then click the Move Up or Move Down button (usually the up or down arrow icon).