generally use pdf2text -layout to convert text to pdf in Linux command line then import the text file into R. For working with tables I use tabulizer to extract the tables in the browser though there also are native python and R bindings. You might also use pdftools on CRAN for importing PDFs but in my experience that requires more wrangling than creating a text file using pdf2text or tabulizer externally.
https://datascienceplus.com/extracting-tables-from-pdfs-in-r-using-the-tabulizer-package/