Sure. Use PDFSharp to do this:

```
PdfReader first = PdfReader.Open("file1.pdf", PdfDocumentOpenMode.Import))
PdfReader second = PdfReader.Open("file1.pdf", PdfDocumentOpenMode.Import))

for (int i = 0; i < second.PageCount; i++)
        first.AddPage(second.Pages[i]);

second.Save("output.pdf")
```
spam fails_task lang_mismatch pii not_appropriate hate_speech sexual_content quality toxicity humor helpfulness creativity violence