Where do downloaded PDFs go on my iPad?

PDFs are usually downloaded into the Files app, though it is also possible to load the PDF into the Books app.

Hello Kkurpik!

Please see this Support Article for information on where “downloaded pdf's go on my iPad”:

Save and edit PDFs to the Books app on your iPhone or iPad - Apple Support

I hope this is helpful. Good Luck!

When there have been recent downloads, you can view the downloads using the following (this image from iPad running iPadOS 16) highlighted button:

I don’t have any devices as far back as iOS 9 to check this, though.

As MrHoffman pointed out, you can also save, organize, and share files in the Files app.

Thank you MrHoffman.