How to merge PDF files for free?

(For the latest PDF files Merger Software please have a look at the top of the left margine, inside the red box.) Google has advised me to write a blog with this title to help search engine crawlers find this place for relevant software. Since if I do not put that question directly on the title then search engines are not able to recognize that. I wrote this software as a demo and for my personal usage many years ago, perhaps 2003 or 2004. I had not any idea that it could be of some assistance to public. Recently, my daughter, mentioned me that it could be useful making it available for public. When I put it here, swiftly few hundred downloads reported to my blog stat in Google Analytic. Having noticed the interest, I started to test the software with the stress tests of a user not the way that I could use it personally and I noticed many bugs in it. Immediately I removed the bugs and deprecated the alpha version. Then I received few further issues and on a nightly basis newer versions uploaded to Messiah's Site. A help and issue page also was established. I noticed that for a full utilization of the software I needed to have a PDF file splitter and a software to inject a PDF file into a certain page of another PDF file. Some of the users kindly have advised me for creating some other PDF software. I am a retired teacher and a retired System Analyst. But to fulfil that demand I am busy to do that task. I have two gadgets at hand right now that prevents my full-time endeavour on the PDF software. One is related to control systems theory which I have written in java language at the moment but I like to rewrite it in assembly code to be readily usable for embedded systems and the other is an educational gadget. All will come free on public domain. So obeying the advice to help the crawlers to come here I have a humble answer for "How to combine PDF files, how to join PDF files, how to split PDF files and how to insert one PDF file inside another PDF file."

Update, May 2016 : Dysprosium (Dolce edition) has been released (please click) based on iText from mid of April 2014 and smoothly on a nightly basis added more features and now I have deprecated many scattered pieces of PDF utilities I already released. There are so many features that I cannot write complete instructions for all of them. From other previous pieces only Signature manager has been remained to be integrated. I sorted out PDF viewer problem somehow satisfactorily.)

(updated : 26/May/2016) I have had over 60,000 downloads from 187 countries. All around the world, only 1 country in South America (French Guiana) and 1 countries in Asia (Democratic North Korea ) have not used Dysprosium Software, yet. The remaing countries not downloaded to this date (less than 10) are from the central Africa and perhaps some very small Island countries.