To password protect a PDF in Adobe Acrobat Reader, you'll need the paid Pro version, which starts at $14.99 a month.
You can save any PDF onto an iPad, and read them in apps like Apple Books and Google Drive. Here's how to save PDFs on an iPad, with specific steps.
In the top menu of Excel select Data > Get Data > From File > From PDF. Browse your files and select the PDF with the table ...