Let's say that you want to share a link to a PDF that is available online, but you want viewers to visit a specific page of that PDF.
You can append "#page=" and then the page number to the end of any PDF online to create a URL that takes viewers directly to the page you specified.
EXAMPLE:
The College Board hosts a PDF of SAT Practice Test 1 on their website at this link: https://satsuite.collegeboard.org/media/pdf/sat-practice-test-1.pdf
If I want someone to open the test to Section 2, which begins on page 20, I can add "#page=20" to the end of the URL.
https://satsuite.collegeboard.org/media/pdf/sat-practice-test-1.pdf#page=20