Sorry for the delay in response.
To generate a public link, open a PDF and then click on three dots as shown in the screenshot below:
Then select share and click on "make public" tab you get on next page at bottom.
If you are not able to view that option, try to swipe up from bottom.
After the link is generated, you can select the option where you want to share that link.
Let us know if you need any help.