PDF (Portable Document Format) is a versatile electronic document format. It was initiated by Adobe and was originally intended for electronic presentation of printed materials. Hence, the tasks of this format follow - storing information about the color scheme and the arrangement of elements, as well as ensuring identical output on different monitors and printers. PDF documents can be opened using the free version of Adobe Reader or a web plug-in that is available for most Internet browsers. In some browsers, in particular, in Google Chrome, this format is supported even without the plugin installed. You can edit PDF files using the paid version of Adobe Reader. Also, there are a huge number of programs for both opening and working with this format, and for converting to other formats.
PNG (Portable Network Graphics) is a popular internet raster graphics file format that uses lossless compression technology and supports translucency (alpha channel). You can make a picture in PNG format using any graphics editor (including Paint and Photoshop). The PNG format contains a specific palette of colors used in a drawing. A similar graphic format is quite often used on the World Wide Web when endowing web pages with various images. By using the Deflate compression algorithm, bitmaps with the PNG file extension are available for compression without any apparent quality loss.