Organising pages
Why does my PDF look right on screen but print sideways?
Because rotation in a PDF is a flag attached to the page rather than a change to the page itself. Most viewers apply it and some printers and tools ignore it, so the fix is to bake the rotation in rather than to keep flipping the view.
This is confusing because the screen and the printer are both following the file. They read different parts of it.
Two different ideas of "sideways"
A PDF page has a size: a width and a height in points. An A4 page in landscape is 842 × 595, wide and short.
A PDF page also has a rotation: a number (0, 90, 180 or 270) attached to the page that says "show me turned". The content itself doesn't change. The page is still stored as portrait, with a note to show it rotated.
Both give you a landscape-looking page on screen. But they are different, and programs don't all treat the second one the same way.
Where the disagreement bites
- Viewers almost always follow the rotation. That is why it looks right when you open it.
- Printers and print drivers usually follow it too, but not always. A driver set to "fit to page" may fit the *unrotated* page.
- Other tools (merge, split, stamp, extract) vary. Some keep the rotation, some drop it, some apply it and some ignore it.
So a file that looks right everywhere you have checked can still come out of a printer, or a colleague's process, turned ninety degrees.
The fix: save the rotation into the page
Change the page itself so no program has to read a note. Rotate PDF saves the rotation into the document, so the page is stored the way it should look and every tool after it sees the same thing.
To check it worked, close your viewer, reopen the file, and make sure it still looks right. If a rotation only lasts until you close the file, it was a view setting and the file never changed.
A common trap: rotating in a viewer
Most PDF readers have a rotate button in the toolbar. That only changes the view. It turns what is on your screen, not the document. Closing the file forgets it, and printing may ignore it. If your rotation keeps "not saving", this is almost always why.
When the page is the wrong size, not the wrong way up
If content is being cut off instead of turned, rotation is not the problem. The page is a different size from the paper, and that needs a different fix: see A4 versus Letter and Resize PDF.
Common questions
Why does my rotation disappear when I reopen the file?
Because it was a view setting in your reader, not a change to the document. Rotating with a tool that saves the change into the page makes it permanent.
Can I rotate only some pages?
Yes. Scanned documents often have a few pages fed in the wrong way, and rotating only those is the most common case.