Crop and align each site of a pdf document

I scanned several pages of a book and saved it as pdf. Now I want to crop and align each single page of this pdf (scans are not nicely aligned and show the edge of the book). Since Acrobat only allows to rotate in 90 degree steps, I decided to do it in Photoshop. Now each pdf page is available as one indpependent file in Photoshop. How can I save/export the Photoshop files again in one pdf document, after processing?
Or is there a better way to do it?
By the way I'm using Adobe CC.
Thank you in advance for the help