PDF operations like merging pdfs, adding bookmarks and compression

You can use the PDFFile MergeFiles method to merge pdfs. The WriteBookmarks method can be used to add a bookmark. For compression, you can use the PdfCompressorEngine SetCompression method to adjust what kind of compression you would like done. Here is documentation which demonstrates this implementation:

https://www.leadtools.com/help/sdk/v22/dh/pdf/pdffile-mergefiles.html

https://www.leadtools.com/help/sdk/v22/dh/pdf/pdffile-writebookmarks.html

https://www.leadtools.com/help/sdk/v22/dh/pd/pdfcompressorengine-setcompression.html

You can check Free Spire.PDF which supports all functions you mentioned. But note that it has a limitation of 10 pages.

https://www.e-iceblue.com/Introduce/free-pdf-component.html

 

Merge PDF

https://www.e-iceblue.com/Tutorials/Spire.PDF/Spire.PDF-Program-Guide/Merge-PDF-Files-with-New-Method-in-C.html

 

Add bookmarks:

https://www.e-iceblue.com/Tutorials/Spire.PDF/Spire.PDF-Program-Guide/PDF-Bookmark-Add-PDF-Bookmark-in-C-VB.NET.html

 

Compress PDF:

https://www.e-iceblue.com/Tutorials/Spire.PDF/Spire.PDF-Program-Guide/Document-Operation/How-to-Compress-PDF-Document-in-C-VB.NET.html 

Finding free s/w to perform operations on pdf is rather difficult and when you understand these operations then you know why.

 

Anyway, just to give you some head start, you can start looking into PdfTk (or pdf toolkit). Note that it has command line interface, which means you can use it from within C# but it will run within it's own process space. 

 

https://www.pdflabs.com/ 

 

Hope it helps!