There are several ways to open a PDF file under Linux or FreeBSD. Here are some common options:
To open a PDF file with one of these applications, simply double-click on the file in your file manager, or use the open command followed by the name of the file:
open /path/to/myfile.pdf
Use a web browser: Most modern web browsers can display PDF files natively. To open a PDF file in your web browser, simply click on the file in your file manager, or enter the file's URL in the address bar of your browser.
Use the pdftotext command: The pdftotext command is a command-line tool that converts PDF files to plain text. To use it, simply run the pdftotext command followed by the name of the PDF file and redirect the output to a text file:
pdftotext /path/to/myfile.pdf > myfile.txt
You can then open the text file in a text editor or word processor to view the contents of the PDF file.
pdfinfo command: The pdfinfo command is a command-line tool that displays information about a PDF file, such as the number of pages, the author, and the title. To use it, simply run the pdfinfo command followed by the name of the PDF file:pdfinfo /path/to/myfile.pdf
This will display the information about the PDF file on the terminal.
Keep in mind that these are just a few of the many options available for viewing PDF files on Linux and FreeBSD. For more information and other options, you can refer to the documentation for your specific operating system or the man pages for the relevant command-line tools.