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In Acrobat, to add files to a new PDF file, click Tools and choose "Combine Files. If you then click "Add Files," you'll see an Explorer or Finder window, but you can also just drag and drop files into this webpage to upload them.
It may take several seconds or even minutes for Adobe to generate thumbnail images of your files on the following page. Once this is done, you can quickly rearrange the order of the files by dragging and dropping. You can also do this later on, but it's quicker to do it now.
Once you are satisfied with their order, click "Combine," and Adobe will generate a single PDF file using these documents.
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Once you have files assembled into a PDF file, you can rearrange them in several ways. Click the "Organize Pages" icon on the right toolbar. (Or, click Tools → Organize Pages.)
Adding Another File
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To add a file to a PDF, on the Organize Pages screen, click Insert at the top, and choose "From File..."
You can then find and add the file or files from your Hard Drive.
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Rotate pages by clicking on the page to highlight it. A small menu appears; click the circle-arrow icons to rotate the page image in either direction.
Organization via Bookmarks and Thumbnails
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If you right-click on a bookmark, you get a variety of different options, including to delete or change it's destination (where it goes when a reader clicks it.) Probably most useful is "rename," since you may want more descriptive headings than your file names.
You can also manually add bookmarks:
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