How Do I Read And Modify PDF File Using Java?

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How do I read and modify PDF file using Java?

The answer is pdfminer as others have said, but if the libraries aren’t working for you, it’s likely because you are expecting too much from them. You need to understand how the pdf file format works, as opposed to how text format works. Specifically, we all expect to be able to use a library to parse some file format for text and be able to iterate through the text line by line, but what if the text has no line characters? How would the library know what constitutes a line? Most libraries won’t try to guess at that, and honestly we wouldn’t want them to, because if the line isn’t represented by a line character, then the concept of line isn’t really part of the text (is it?) and we are using the library to extract *text*. In pdf, text is laid out, meaning that a particular text object get displayed at a particular x,y position on the page. So what you might think of as 3 lines would actually be 3 text objects, displayed at (x,y), (x, y-20), (x, y-40), so a text extraction library would just pull out the text, but you’d have no line data. (IRRC pdfminer hands you String as output, just a big String, not a (line) iterable, it was because PDFMiner didn’t work for me that I had to study up and learn a bit about pdf to get what I wanted out of the files). The upside is this — You finally get a chance to ‘roll your own.’ Fortunately, extracting the text out of a pdf is very well defined and simple goal. And fortuanately, PDF is a very well documented and very well understood file format, so google is going to be very helpful. If push comes to shove, the text rendering part of the spec is less than 200 pages, but you won’t need to go there. Start here. Introduction to PDF Then read the wikipedia article which is super well written. Then you will have to open the file in text editor and study it, which won’t be hard if you are interested only in text. Use this as a tool to understand the stream writing operators. Online Pdf Writer Portable Document Format The accepted answer to the following SO tells you what you need to investigate to understand how text is encoded within the pdf. Programatically rip text from a PDF File (by hand) - Missing some text Google anything you wish to understand, and you will be brought to cool sites like planetpdf, where t have great articles. It should take you a day or two to hand write your parser and you will learn a lot in the process about something pretty common. The libraries have to be general, so t are going to be limited. (perhaps irrelevant, the pdfs I was working with are linearized—see the linked references—which made studying the text in the pdf and mapping to the layout on the screen super simple, I didn’t study an non-linearized files because i didn’t have to, but if it makes things harder there’s a ton of code out there to linearize a pdf but not a lot out there that can go the otherway)

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What you will get, hopefully, is enough knowledge to write your own PDF parser, or to extend what you have already written to create new versions. What this is not, is a tutorial on developing a standalone parser. This is a tutorial on making parsers for PDF files. A PDF parser needs two inputs: the input string, and the PDF file. A PDF parser will try to extract one of these two (and sometimes a third). (if you are using other parsers, there are going to be some differences, a basic parser will use a different PDF parser and vice versa. It doesn’t make much sense for you to learn how to use these libraries if you aren’t making them yourselves, and a PDF file is already parsed to start with, and that means you should already understand how one works.