Ways to Split PDF file into Multiple files and Pages in Java

SplitPdfByRange.java

/*
 * Split PDF file by Given Range into Single Page files in Java
 */
// Load the PDF file
Merger merger = new Merger("path/document.pdf"); 

// Define output file(s) format
String filePathOut = "path/splitPDF_{0}.{1}";

// Define Range to extract as single page documents
SplitOptions splitOptions = new SplitOptions(filePathOut, 3, 7);

// Split PDF according to split options
merger.split(splitOptions);

SplitPdfByRangeAndFilter.java

/*
 * Split PDF file by Given Range & Filter (Even/Odd Pages) into Single Page files in Java
 */
// Load the PDF file
Merger merger = new Merger("path/document.pdf"); 

// Define output file(s) format
String filePathOut = "path/splitPDF_{0}.{1}";

// Define Range & Filter to extract all the ODD Pages in the given Range as single page documents
SplitOptions splitOptions = new SplitOptions(filePathOut, 3, 7, (Integer)RangeMode.OddPages);

// Split PDF according to split options
merger.split(splitOptions);

SplitPDFintoMultiPageFiles.java

/*
 * Split PDF files into multiple page files in Java
 */
// Load the PDF file
Merger merger = new Merger("path/document.pdf"); 

// Define output file(s) format
String filePathOut = "path/splitPDF_{0}.{1}";

// Define Splitting Intervals and Split Mode
SplitOptions splitOptions = new SplitOptions(filePathOut,  new int[] { 3, 6, 8 }, SplitMode.Interval);

// Split PDF according to given intervals
merger.split(splitOptions);

SplitPDFToSinglePages.java

/*
 * Split PDF file into Single Page files in Java
 */
// Load the PDF file
Merger merger = new Merger("path/document.pdf");

// Define output file(s) format
String filePathOut = "path/splitPDF_{0}.{1}"; 

// Define pages to get extracted as single page document
SplitOptions splitOptions = new SplitOptions(filePathOut, new int[] { 3, 6, 8 });

// Split PDF according to split options
merger.split(splitOptions);

@gsammatrice

Please have a look at the free trial limitations. However, you can avail a temporary license that is actually a time-restricted full license. Follow the steps mentioned in this forum thread.
Apply license as follows:

// Setup license.
License license = new License();
license.SetLicense(@"D:/LicensePath");

If issue persists, please share the complete exception stack trace. Secondly, are you working with multiple GroupDocs APIs (e.g. GroupDocs.Conversion for .NET) in a single project?