I think it is popular because it was the first widespread format that everyone had. It was the same file across different operating systems. And possible for third parties to create writers for (word is not). It also prints in a predictable manner.
Adobe PDF Reader is free. People aren't paying for it. One could argue that Microsoft Word Reader is free too. But it isn't as widespread.
Once upon a time, M$ came out with "password protected doc files". Unfortunately they could be opened with wordpad without any password!
One of the projects I worked on, included generating reports for the client. The fact that pdf could not be easily "edited" was one of the plus points. Also the fact that pdfs could be generated via Java (using iText). Add to it the cost factor Jeanne mentioned.
Microsoft tried to create their own PDF-like format (named XPS) but it has not caught on, because the whole world already uses PDF.
Word documents are not a good replacement for PDF, because Word is not free and not everybody has Word or even Microsoft Windows. Also, Word documents are normally editable, and I'd argue that one of the advantages of PDF is that it's normally read-only. And as Jeanne says, it prints in a predictable manner, and documents on screen look (almost) exactly as how they are printed.
but google also giving free office documents rite, why those also not popular
Google Docs is only free once you've paid for always-on internet connectivity. And you get no guarantees as to uptime and data availability (I think, haven't checked the SLA if you pay for the service). The recently publicized hacking of Google Mail probably won't help, either.
People get locked into certain technologies, and then stick with them, partly because of comfort, and partly because of what Bill Gates has called "positive feedback loops". Frankly, this helps Microsoft more than it hurts them, but in the case of PDF, Adobe came up with a system of creating read-only documents and blasting free readers out to everyone in Christendom. Now you can get free readers for Word, but it's too late. Everyone has the Adobe reader already, so why change? Also, people are used to PDF being read-only or read-mostly documents (like forms).
Does Microsoft offer a Word viewer for Mac/Linux? If not, that is a huge disadvantage. It's also too late. Adobe has the market and one has to offer something new to upset it.
I do not view Google Office as a replacement for Word/Open Office let alone a replacement for PDF. If I can't view my document on a plane/subway/when the net is down, it is not useful to me as a portable/storage format.
Word's kerning is awful; its layout capabilities are sad in general. Word documents just generally look like crap. It's possible to make PDFs that look like crap, too, of course, but it's possible to make PDFs that don't, and that's the key. Reading Word documents for any period of time is just plain painful on the eyes.
ankur rathi wrote:Why pdf format is popular?
Is that because people can't change the content, easily?
No, it's because no matter what platform you're using, the pdf will look the same. Back in the day, font installations could vary drastically, and if the application that created your document couldn't find its fonts on the machine where the document was opened, it was UnHappyLand. pdf allows you to embed the font in the document, so it doesn't matter whether it's installed on the viewer's machine.