art theme Quad band phones, or international phones as is also sometimes called, use four bands and may provide from any location. If you are looking to start a mobile phone business and you wonder what exactly is an unlocked phone guaranteed to sell well and give you minimal trouble with customers it's going to probably be such a cellphone. PDF: Stands for Portable Document Format which is used mainly for documents. PDF file format preserves fonts, page layout, and also other document information and will be imported into Photoshop for editing. PDF files are platform independent, meaning almost any computer OS can be used when opening them. PDF files aren't used in Photoshop for creating artwork.