What is the difference between a PDF and a JPEG file?
Answer: PDF (Portable document format) is a document standard developed by Adobe. It allows scalable text, vector images, and bitmaps to be combined in one document. PDFs can also have multiple pages and embedded fonts. If you open a PDF in Acrobat Reader, for example, you can scale the document to be much larger than the actual size. Because PDFs save the actual text with the document (it is not rasterized), the text will look clean and sharp no matter how much you scale the page. The same is true for vector images in the document, as they are made up of paths, not pixels. Bitmap images, however, will become more and more blocky the larger you scale the document.
JPEGs are bitmap images. This means they will look blocky if you scale them larger than their actual size. They are also compressed, meaning they are not quite as clear as BMP, TIFF, PICT, or other bitmap files, but they take up significantly less space. JPEGs cannot include paths, text, or embedded fonts like PDFs can. For this reason, PDFs are the best choice for saving documents that include text or vector images (paths). Bitmap images, such as those taken with a digital camera, are typically saved in the JPEG format. Most pictures you see on the Web are JPEGs.
PDFs and JPEGs are both cross-platform, meaning they will look the same on a Mac as they do on a Windows PC. While the formats have significant differences, most picture viewing programs can open JPEGs and PDFs. Mac OS X has built-in support for PDFs, allowing documents to be saved as PDFs from the Print dialog box. To create a PDF from scratch, however, you'll need to use Adobe Acrobat. Just about any image editing program will allow you to save your document as a JPEG.