I mean saving them as a pdf and keep them as a backup for future reference or for future reading
There are online converters such as:
In case you are using firefox browser, this addin is a good one:
This is my favourite - converts everything (documents, websites, emails etc)
I have used wkhtmltopdf to convert a webpage to PDF in the past.
If you'd like to save web pages for future reference or future reading I find best to use the Scrapbook Addon in Firefox or save the webpage as .mht file (native in IE, possible in Firefox using UnMHT Addon).
These methods will save your page with more accuracy than printing them to pdf.
I hope it helps.
HTML-to-PDF is a free utility for batch converting webpages to PDF documents from the command line or via a GUI...