I've created my file in X software. I can print on my home printer with this file format. Why do I need to send a PDF?
The main reason is formatting. Each computer is set to display the specific document on screen as you see it. Have you noticed that if you take a file from your work computer and take it and display the same file on your home computer, that some of the formatting has changed? It is the different versions of the same software, on different version of computers that are causing the reformatting issues.
This is especially true with different kinds of type or fonts. If one computer has a type that you found you would like to have in your document, but you send your file to another computer that does not have that type installed, then the software on the new computer will substitute the type to a default type for that software. This happens in print shops everywhere. Unfortunately, on the printers end, they do not notice a difference because they do not know what the original looked like on your computer with your software. Often, the printer is to blame for a funny looking document, when it is just the different computers specific formatting specifications. This is why printers recommend proofing your documents, because you are the only one who knows what the original document looks like. Saving your file as a PDF will alleviate formatting issues. The PDF will lock everything as if it were an image. So there are no formatting or type issues.
The commercial printers of today are modern marvels, creating masterful printed pieces that you cannot print on your home printer. They have many capabilities that your home printer cannot do. So why send a PDF? The print drivers on commercial printers can be picky on the types of files they receive. Some print drivers will attempt to read the data from your current software and try to print it causing coloring issues as well as not printing sections of your document. If the print driver cannot correctly read all of the data, then substitutions will be made.
What about JPG? This file formats usually has a resolution of 72dpi. This is 72 dots per inch, and is best for screens. Printing machines, whether commercial or your home printer print best at 300dpi. You may say that your JPG printed just fine at home. And it probably did. If you were to closely inspect your document, you may notice that it may not be as clear as you saw onscreen. That is the difference in how many dots were printed in one inch. If you save your JPG at 300dpi, then your JPG will print very clearly. Be on the safe side though and please save your JPG as a PDF.
What about PNG's? This file format has a resolution of 72dpi and is for screens and creating smaller files for the web so that your browser will load faster. Please do not send us PNG's. They do not contain enough data for the printer to read. The print driver will reject this type of file.
No matter which software you use, it is still best to save as a PDF.