![]() Some are better than others, and are more able to use more complex features of the language to create more reliable PDF programs or smaller PDF programs.īut applications that write PDF programs also must be able to understand what the source display is all about. Any application that displays what is in a PDF has the objective of being able to run PDF programs to reliably duplicate what the author of those programs intended to be seen.Īpplications that write PDF language obviously must understand how to use that language correctly. ![]() Whenever an application creates a PDF it is writing a program in PDF language that has the objective of duplicating a given display. Clever though PDF language may be, it cannot cover all the bases, and the PDF spec allows different applications to try to program how to duplicate a display using very many different possible programs. The problem with all that is that there is no other program that does everything exactly the way Word does except Word. Adobe PDF language is designed to get around that by writing a program that can, in theory, better mimic what Word would display without requiring Word. ![]() But that only works for an image at a given resolution, when Word can print to printers with higher (sharper text) resolution or lower (blurrier text) resolution. The image is then what it is, a sea of pixels, that represents what the document looks like. One approach to reproducing a document that Word creates is to create an image at some resolution. How a given program like Word does that might be very different than how some other program does that. It composes a paper sheet of a given size, applies a font that has all sorts of graphical characteristics, aligns text into lines and paragraphs with very subtle spacing and margins and all that, and it applies zillions of effects. Word doesn't just take letters and number and print them like a 1960's teletype might. If that sounds complicated and error-prone, it is.īut when you consider how it is that Word does something even as simple as displaying some text in a document, well, it's not that simple. The idea is that if you have an application like Microsoft Word, which displays data in visual form to appear as a document, Word can automatically write a program in PDF language that, when containing within it an encapsulated chunk of subject data, can be run by a PDF interpreter to follow the instructions in the PDF program to take that data and display it the same way Word does. For the most part that usually is all about how to format, scale, transform, edit and display the packet of data that is encapsulated within the PDF file along with the program, but it can be just the execution of programming instructions to create totally new items for visual display. When a different application displays a PDF file, what it is really doing is executing that program, following the instructions in the PDF programming language to create a visual display. When an application creates a PDF file, what it is really doing is writing a program and putting that program into a file along with some data upon which that program works. PDF is a language for working with and for creating visual displays of data that is often found within documents, such as text, or images. PDF is not a format but a language, like Visual Basic or C#. Some background, and a somewhat simplified to avoid going into all the intricacies: I don't understand the effective difference between 'export to PDF' and 'print to PDF' and why one or the other would be preferable (mikedufty indicates 'export' works better).
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