PDF not opening in IPhone 8 Mail or WhatsApp

Hi Guys

i cannot open PDF in my IPhone 8 on Watsapp and Mail. When I try to open the PDF it asks me to select the app that I want the PDF to open but I cannot find iBooks or PDF reader in the option. I have also tried to add the PDF reader and iBooks but I can’t find the option to add them.

The PDF in mail is not working since I updated the iPhone last week but PDF in watsapp is not working since 6 months now.

belown is how it looks when I try to open PDF in mail.

below is how PDF looks when I try to open in WhatsApp.

could you plz solve my issue as this Is really annoying.