PDF (short for Portable Document Format) was created as a format that is a digital equivalent of documents. In this format, all elements of the document are saved as an image, which is composed of individual elements (text, graphics) and their settings (fonts, layout, etc.). With PDF, you can do everything you need as with a regular document — view, edit, print, send to other people.
To view PDF files, there are many programs. The most popular of them is the official program from the company-developer of the format - Adobe Reader (or the paid version of Adobe Acrobat). There are also various plug-ins for Internet browsers, as well as mini-programs for viewing embedded in the web pages.
Files with the .pdf extension can consist of several pages combined into one document, which is very convenient. But if you need to convert the document pages into separate images, it is more convenient to use the JPG format, instead of PDF.