The Marugoto series (also by Japan Foundation) offers free online access to their "Starter (A1)" and "Elementary 1 (A2)" levels via the website. No PDF download, but full interactive content.
If you are looking for digital versions of the full textbooks (Shokyuu, Sho-Chukyuu, or Chukyuu), they are often hosted on document-sharing platforms: Dekiru Nihongo Pdf
Approximately ¥2,800 – ¥3,500 per textbook (around $19–$25 USD). The workbook is extra. The Marugoto series (also by Japan Foundation) offers