Hi Jakko.
If you check the following UK website
wireless-set-no19@groups.io
and look for the Mystery British Wireless Set thread under ‘Messages’ you will find the link to the 4-page PDF that was posted. I have no problem at all opening that link to view the PDF, however it will not let me save the PDF or print it, and if I copy the link and paste it to my Browser, I end up at the PYE Museum website viewing the info you posted here, which is completely different from the PDF.
David