As you read this site, you will see a motif in our praise of the PDF format.  It has its pros and cons, but overall, it makes submitting a digital file to a printer considerably more reliable.  This is largely because a "press quality" PDF file includes all the supporting files necessary for output.  This means you don't have to worry if we have the font you used to design your file, or whether your document will look different on our screen than yours. 

So how do you make a PDF?  On any program, hit File: Print.  If you have a printer-looking icon called Acrobat Distiller, or something with PDF in its name, it's probably your PDF writer.  Printing to it will create a PDF.  If it gives you any options, choose "press quality" and "300 dpi".  Mac OSX supports PDF natively, which means you should just be able to hit File Save As PDF in most programs...

Now to dilate back a step.

Portable Document Format (PDF) is a file format created by Adobe Systems, and fundamentally for document exchange. (Adobe makes all the big production software also, so that adds in compatibility also.)  PDF exists to represent documents in a manner independent of the application software, hardware, and operating system.  Each PDF file encapsulates a complete description of a document that includes the text, fonts, images, and vector graphics which the documents contain.  PDF is an open standard that is read and written by many programs and up to 90% of computers. 

In later PDF revisions, a PDF document can also support links (inside document or web page), forms, JavaScript (initially available as plugin for Acrobat 3.0), or any other types of embedded contents that can be handled using plug-ins.  PDF 1.6 supports interactive 3D documents embedded in the PDF.

While most every computer can read a PDF, you need special software to create a PDF.  If you are on a Macintosh, you can always just "Save as PDF" in any program.  On a PC, you'll need an external program, such as Adobe Acrobat (the professional answer), or the free CuteFTP, which is what we use on every machine for which we don't own a copy of the full Acrobat.  Most of you read your PDFs through the free Adobe Acrobat Reader--even if you don't know you have it, you probably do.

The PDF file format has changed eight times, as new versions of Adobe Acrobat were released.  It doesn't matter which version you use--they are all backwards-compatible.  The newer versions work a bit better, but more than anything, create more efficient files.  So your 10 MB Word file could be compressed to a 1 MB PDF.

Oh, and we can scan to searchable PDF!  That means if you have a contract you want to keep on file, or you're a mortgage broker and have 1000 pages a day of contracts, or a school teacher who is afraid to throw away a growing pile of students' work; you can put that stack through our sheet feeders and walk away with one (or more) PDFs with the whole stack of pages on it.  Put that on your keychain thumbdrive and you'll have every important document, from your renter's contract to your bank statements, on you at all times.

Anyone may create applications that can read and write PDF files without having to pay royalties to Adobe Systems; Adobe holds patents to PDF, but licenses them for royalty-free use in developing software complying with its PDF specification.

PostScript is a page description language run in an interpreter to generate an image, a process requiring many resources. PDF is a file format, not a programming language, i.e. flow control commands such as if and loop are removed, while graphics commands such as lineto remain.

Vector graphics in PDF, as in PostScript, are constructed with paths. Paths are usually composed of lines and cubic Bezier curves, but can also be constructed from the outlines of text. Unlike PostScript, PDF does not allow a single path to mix text outlines with lines and curves. Paths can be stroked, filled, or used for clipping. Strokes and fills can use any color set in the graphics state, including patterns.

PDF supports several types of patterns. The simplest is the tiling pattern in which a piece of artwork is specified to be drawn repeatedly. This may be a colored tiling pattern, with the colors specified in the pattern object, or an uncolored tiling pattern, which defers color specification to the time the pattern is drawn. Beginning with PDF 1.3 there is also a shading pattern, which draws continuously varying colors. There are seven types of shading pattern of which the simplest are the radial shade (Type 2) and axial shade (Type 3).

Normally all image content in a PDF is embedded in the file. But PDF allows image data to be stored in external files by the use of external streams or Alternate Images. Standardized subsets of PDF, including PDF/A and PDF/X, prohibit these techniques.  What does that mean to you?  A PDF will work, but it's always smart to give us the images and fonts you used to create it also.

Text in PDF is represented by text elements in page content streams. A text element specifies that characters should be drawn at certain positions. The characters are specified using the encoding of a selected font resource.

A font object in PDF is a description of a digital typeface. It may either describe the characteristics of a typeface, or it may include an embedded font file. The latter case is called an embedded font while the former is called an unembedded font. The font files that may be embedded are based on widely used standard digital font formats: Type 1 (and its compressed variant CFF), TrueType, and (beginning with PDF 1.6) OpenType. Additionally PDF supports the Type 3 variant in which the components of the font are described by PDF graphic operators.

PDF 1.4 allows transparencies.  Previous versions do not.  Long and short means if you don't flatten your file before export, occasionally you'll end up with layering issues in a complex file--they will show up fine on screen, maybe even printed on your printer, but randomly won't on a high end printer with a pre-1.4 postscript engine.  That only applies to spot colors in postscript intensive files, i.e. from Illustrator.  If you don't know what that means, it's not statistically common enough to worry about.

A PDF may contain structure information to enable better text extraction and accessibility.

Compared to the PostScript format, PDF lacks e.g. the notion of "tray selection"; this can be used to indicate that some pages of a document must be printed on a different type of paper.  Such features are not omissions from the PDF format, whose scope only covers electronic documents. The JDF standard covers such aspects; however, it is a complex standard, which as of 2007 is still not widely implemented. This hinders the replacement of PostScript by PDF.

Two PDF files that look similar on a computer screen may be of very different sizes. For example, a high resolution raster image takes more space than a low resolution one. Typically higher resolution is needed for printing documents than for displaying them on screen. Other things that may increase the size of a file is embedding full fonts, especially for Asiatic scripts, and storing text as graphics.

There are fourteen typefaces that have a special significance to PDF documents: Times Roman (in standard, italic, bold, and bold italic), Courier (in standard, oblique, bold and bold oblique), Helvetica (in standard, oblique, bold and bold oblique), Symbol and Zapf Dingbats. These should always be present (actually present or a close substitute) and so need not be embedded in a PDF. PDF viewers must know about the metrics of these fonts. Other fonts may be substituted if they are not embedded in a PDF.

Readers for many platforms are available, such as Adobe Reader, Foxit, Preview, Sumatra PDF, Xpdf, Evince, Okular, KPDF, Drumlin PDF reader, Embedded General EG-DocViewer PDF and ePDFView; there are also front-ends for many platforms to Ghostscript. PDF readers are generally free.

There are many software options for creating PDFs, including the PDF printing capabilities built in to Mac OS X and some versions of Linux, the multi-platform, Microsoft Office 2007 (via a Microsoft-produced add-on), Wordperfect since version 9, numerous PDF print drivers for Microsoft Windows, the pdfTeX typesetting system, the DocBook PDF tools and Adobe Acrobat itself.

There is also specialized software for editing PDF files, though the choices are much more limited and often expensive. Adobe Acrobat Professional is one example of software that allows the user to annotate (highlight, add notes to) already created PDF files. A free one is PDFedit. As of version 0.46, Inkscape also allows PDF editing through an intermediate translation step involving poppler.

PDF was selected as the "native" metafile format for Mac OS X, replacing the PICT format of the earlier Mac OS. The imaging model of the Quartz graphics layer is based on the model common to Display PostScript and PDF, leading to the nickname "Display PDF". The Preview application can display PDF files, as can version 2.0 and later of the Safari web browser. System-level support for PDF allows Mac OS X applications to create PDF documents automatically, provided they support the Print command. When taking a screenshot under Mac OS X versions 10.0 through 10.3, the image was also captured as a PDF; in 10.4 and 10.5 the default behaviour is set to capture as a PNG file, though this behaviour can be set back to PDF if required.

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