To cite package ‘pdfminer’ in publications use:

  Schwendinger F, Schwendinger B (2020). _pdfminer: Read Portable
  Document Format (PDF) Files_. R package version 1.0,
  <https://CRAN.R-project.org/package=pdfminer>.

A BibTeX entry for LaTeX users is

  @Manual{,
    title = {pdfminer: Read Portable Document Format (PDF) Files},
    author = {Florian Schwendinger and Benjamin Schwendinger},
    year = {2020},
    note = {R package version 1.0},
    url = {https://CRAN.R-project.org/package=pdfminer},
  }