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Table 3.2 Minimum and maximum page size of AcrobatPDF viewer minimum page size maximum page sizeAcrobat 4 and above 1/24" = 3 pt = 0.106 cm 200" = 14400 pt = 508 cmAcrobat 7 and above withthe userunit option3 user units 14 400 user unitsThe maximum value 75 000 for userunit allows page sizesup to 14 400 * 75 000 = 1 080 000 000 points = 381 km> MediaBox: this is used to specify the width and height of a page, and describes whatwe usually consider the page size.> CropBox: the region to which the page contents are to be clipped; Acrobat uses thissize for screen display and printing.> TrimBox: the intended dimensions of the finished (possibly cropped) page;> ArtBox: extent of the page’s meaningful content. It is rarely used by application software;> BleedBox: the region to which the page contents are to be clipped when output in aproduction environment. It may encompass additional bleed areas to account for inaccuraciesin the production process.PDFlib will not use any of these values apart from recording it in the output file. By defaultPDFlib generates a MediaBox according to the specified width and height of thepage, but does not generate any of the other entries. The following code fragment willstart a new page and set the four values of the CropBox:/* start a new page with custom CropBox */p.begin_page_ext(595, 842, "cropbox={10 10 500 800}");Number of pages in a document. There is no limit in PDFlib regarding the number ofgenerated pages in a document. PDFlib generates PDF structures which allow Acrobat toefficiently navigate documents with hundreds of thousands of pages.3.2.3 PathsA path is a shape made of an arbitrary number of straight lines, rectangles, or curves. Apath may consist of several disconnected sections, called subpaths. There are severaloperations which can be applied to a path:> Stroking draws a line along the path, using client-supplied parameters (e.g., color,line width) for drawing.> Filling paints the entire region enclosed by the path, using client-supplied parametersfor filling.> Clipping reduces the imageable area for subsequent drawing operations by replacingthe current clipping area (which is the page size by default) with the intersection ofthe current clipping area and the area enclosed by the path.> Merely terminating the path results in an invisible path, which will nevertheless bepresent in the PDF file. This will only rarely be required.It is an error to construct a path without applying any of the above operations to it.PDFlib’s scoping system ensures that clients obey to this restriction. If you want to setany appearance properties (e.g. color, line width) of a path you must do so before startingany drawing operations. These rules can be summarized as »don’t change the appearancewithin a path description«.3.2 Page Descriptions 57