![]() If the fonts are not available the output may not render properly. This reference may to be to fonts that are enclosed in the file itself or to external fonts that are expected to be available to the rendering software. Text in PDF is referenced to a particular font and font size. A table may also exist as an image in the file. This looks like a table to the reader but it is not possible to reverse the process and extract a table from the data base. It consists of text placed at specific places on the page together with some line graphics. This sets PDF files apart from many other eBook formats because most of the latter provide data that is not constrained to a page boundary or required to conform to placement on a fixed size page.Ī PDF file may contain tables but there is usually no intelligence to a table's construction. It is possible to zoom into or out of a page of data to make it seem larger or smaller using the capabilities of some viewing software. The size and rotation of these pages is determined when the file is built, although it can change from page to page. See OCRmyPDF for a tool that can add text to an image PDF.Ī PDF file, by its very nature, contains pages of information that are to be displayed or printed. However, often it is created via the OCR process and may not match the displayed text due to OCR errors. It provides the ability to search the text in the document. This image/text data may be, and likely will be, stored using JBIG2 compression.Ī PDF file that is made of images may also include a layer of actual text that is not displayed. Text, displayed in this fashion, behaves differently from regular text when the file is manipulated by the display software. For example a PDF file might look like it has text in it while in fact the PDF is displaying images (pictures) that contains text. Not all PDF files contain all of the types of data and some PDF files are different from what they seem. PDFs can also contain links and buttons, form fields, audio, video, and business logic. These include Text, Raster Graphics, Vector Graphics ( SVG), Fonts (Glyphs), and meta data. A half A size works well to display on most devices and can be printed using 2 pages per paper sheet in landscape mode.Ī PDF file may contain several types of data. While a PDF is always arranged by pages there is no reason that a better aspect ratio or smaller size cannot be generated when targeting an electronic device. Most portable devices do not have screens nearly this big so they will often shrink the page to the point of not being readable or zoom in to just part of the page causing the reader to pan the page around to try and read it. To display such a page on a computer or eBook screen at full size would require a 14" or larger screen display. Since PDF is designed for printing it is generally defaulted to letter size for US documents and A4 for Europe (See Paper sizes). ![]() The standard does not encompass all versions or all capabilities. Since it was designed as a print format it specifies the size of the paper that is needed to reproduce (render) the original. Initially PDF was designed as a print format similar to PostScript and even today it is often used to exchange data that will be printed.
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