Is there a Java library for PDF page splitting (not document). The final purpose is to parse text from each of the splits separately.
As an example, let’s say I want to cut every pdf page into 4 pieces vertically — see illustration:

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After clarifying you want to parse text, there is this iText sample ExtractPageContentArea or (as mentioned by @ipavlic) the PDFTextStripperByArea class from the Apache Pdfbox project.