It is published by and comes in two main volumes corresponding to the beginner levels:
"Minna no Nihongo Kanji Renshuuchou" is a popular workbook for practicing Kanji characters, and it's great that you're looking for a PDF version.
PDF, it is widely considered one of the best supplements for mastering the 200+ kanji introduced in the Shokyuu (Beginner) series. Unlike the standard "Kanji Book," which focuses on readings and context, the is designed for pure writing practice and reinforcement. Top Resources to Find & Use the PDF