var ThisPdfDoc := iexPdfiumCore.TPdfDocument.Create;
try
  ThisPdfDoc.LoadFromFile(APdfFile);
  for var i := 0 to ThisPdfDoc.PageCount - 1 do
  begin
    //ThisPdfDoc.Pages[i]. -> Unfortunately, there is no method to extract the text from the whole page!
  end;
finally
  ThisPdfDoc.Free;
end;

FCriticalSectionPdf: TCriticalSection;

function ExtractPdfTextThreadLocal(const FileName: string): string;
begin
  FCriticalSectionPdf.Enter;  // Only ONE thread can enter
  try
    PdfDoc := TPdfDocument.Create;
    try
      PdfDoc.LoadFromFile(FileName);
      // Extract text...
    finally
      PdfDoc.Free;
    end;
  finally
    FCriticalSectionPdf.Leave;  // Release lock
  end;
end;

PdfDoc: TPdfDocument;
PdfDoc := TPdfDocument.Create; 
PdfDoc.LoadFromFile(FileName);

function ExtractPdfText(const FileName: string): string;
var
  Doc: TPdfDocument;
  i, j, CharCount: Integer;
  PageText: string;
begin
  Result := '';
  Doc := TPdfDocument.Create();
  try
    Doc.LoadFromFile(FileName);

    for i := 0 to Doc.PageCount - 1 do
    begin
      Doc.ActivePageIndex := i;
      CharCount := Doc.Pages[i].GetCharCount;

      // Pre-allocate string length for performance
      SetLength(PageText, CharCount);

      for j := 0 to CharCount - 1 do
        PageText[j + 1] := Doc.Pages[i].ReadChar(j);

      Result := Result + PageText + sLineBreak;
    end;
  finally
    Doc.Free;
  end;
end;