PDF or portable document format Software is used to save files that cannot be modified but can be easily shared and printed. All the elements of a printed document are present as an electronic image in this format that you can view, navigate, print, or forward to someone else.
Once a document is saved as a PDF file, it cannot be converted back to a Microsoft Office file format without specialized software or a third-party add-in.
In 1993, it is developed by Adobe to present documents, including text formatting and images, that is independent of application software, hardware, and operating systems. Each PDF file summarizes a complete description of a fixed-layout flat document based on the PostScript language that include the text, fonts, vector graphics, raster images and other information needed to display it. PDF no longer requires any royalties for its implementation as it is ISO standardized.
Features of PDF Software:
- PDF files contain various content such as flat text and graphics,logical structuring elements, interactive elements such as annotations and form-fields, rich media with or without video content, layers and three dimensional objects using U3D or PRC. Various other data formats can also be the part of content in a PDF file.
- Specification are also provided for encryption and digital signatures, file attachments and metadata.
- PDF is created by combining three technologies. These include:
- For generating the layout and graphics, a subset of the PostScript page description programming language is used.
- To allow fonts to travel with the documents, a font-embedding or replacement system is used.
- To bundle these elements and any associated content into a single file, a structured storage system is used. This can be done with data compression.
- The graphics represented in PDF is very similar to that of PostScript. However, the use of transparency was added in PDF 1.4. A device-independent Cartesian coordinate system is used in PDF to describe the surface of a page.
- Text elements in page content streams represents the text in PDF.
- Characters are shown using integers within text strings that map to glyphs in the current font using an encoding. PDF can specify a predefined encoding or the built-in encoding of font to use. It can also provide a lookup table of differences to a predefined or built-in encoding.
- A PDF file can be encrypted for security, or digitally signed for authentication. PDF usually consists of two different methods and two different passwords for security. This include a user password, which encrypts the file and prevents opening, and an owner password, that restrict some operations even when the document is decrypted. Operations such as modifying, printing, adding or modifying text notes, or copying text and graphics out of the document can be done only after giving the owner password. An owner password can easily be removed by software, including some free online services.
- Additional interactive features that are not available by default in a PDF viewer application can be enabled by usage rights (UR) signatures. It can be used to allow a user to save the PDF document along with modified form and/or annotation data, import data files in FDF, XFDF, and text (CSV/TSV) formats, export data files in FDF and XFDF formats, apply a digital signature to existing digital signature form field etc.
- File attachments in PDF files can be accessed and opened or saved to a local filesystem.