To manually crop a picture in Microsoft Word, Excel, or PowerPoint, select it, and in the Picture Format tab on the ribbon, click the top half of the split "Crop" button.

Photoshop offers a wealth of tools for cropping images. You can crop to an aspect ratio, use content-aware fill and many other techniques.

You can crop a PDF on your Windows computer for free using the cropping tool, without having to purchase Adobe Acrobat.