Pdf source file

If you have a scanned page or image, you can use OCR to extract text from your file and paste it into the new PDF document. That way, you can easily convert from image to text. If you find a free converter to turn your files into PDF documents, you should always make sure that your computer or mobile device is safe. By using an online converter, you can be sure that you won't have to download and install any suspicious programs. Say good-bye to worrying about malware, viruses or storage space when converting to PDF.

On PDF2Go, you only download your edited file and nothing else. PDF is a wide-spread and common document format. It's main features are print optimization and a fixed formatting that allows PDFs to look exactly the same on any device. Simply check the "Use OCR" option in this case. If you have safety concerns you will find them eased. We do not obtain the right of your file and there will be no manual checking.

After a certain amount of time, the files will be deleted from our servers. PDF2Go does exactly what the name implies: the online PDF converter works from any device, online, without installation of any additional software. Just use your browser. Rate this tool 4. You need to convert and download at least 1 file to provide feedback. By declaring an object an indirect object, we are able to use it in the PDF document cross-reference table and reuse it by any page, dictionary and so on in the document.

Since every indirect object has its own entry in the cross-reference table, the indirect objects may be accessed very quickly. The object identifier of the indirect object consists of two parts; the first part is an object number of the current indirect object. The second part is the generation number, which is set to zero for all objects in a newly-created file.

This number is later incremented when the objects are updated. We can refer to the indirect objects with indirect reference, which consists of the object number, the generation number and the keyword R. To reference the above indirect object, we must write something like below:. Most of the objects in a PDF document are dictionaries. Page objects are connected together and form a page tree, which is declared with an indirect reference in the document catalog.

The whole structure of the PDF document can be represented with the picture below [1]:. Figure 7: Structure of the PDF document source. In the picture above, we can see that the document catalog contains references to the page tree, outline hierarchy, article threads, named destinations and interactive form. From the picture above, we can see that the Document Catalog is the root of the objects in the PDF document.

It also contains the information that declares how the document will be displayed on the screen. The entries in the document catalog are as follows:. The reader can take a look at our sources for details. An example of the document catalog is presented below: 1 0 obj. The pages of the document are accessed through the page tree, which defines all the pages in the PDF document. The tree contains nodes that represent pages of the PDF document, which can be of two types: intermediate and leaf nodes.

Intermediate nodes are also called page tree nodes, while the leaf nodes are called page objects. The simplest page tree structure can consist of a single page tree node that references all of the page objects directly so all of the page objects are leafs. Each node in a page tree has to have the following entries:. A basic example of a page tree can be seen below: 2 0 obj. We can also see that the leaves of the page tree are dictionaries specifying the attributes of a single page of the document.

There are multiple attributes that we can use when defining them for each document page. Figure 8: Simple document. We can see that the. We can compile the. The resulting PDF then looks like this shown in the picture below:. Figure 9: Result. Fullbanner This is pdfTeX, Version 3.

We also need to remember that all the encoded data streams were removed and replaced with three dots for clarity and brevity. The header can be seen in the picture below:.

Figure PDF header. Figure PDF body. Figure PDF xref. And last, the Trailer section is represented below:. Figure PDF trailer. We presented all of the sections of the PDF document, but we still have to analyze them further. This is why we must first take a look at the xref section. We can see that the offset from the beginning of the file to the xref table is bytes, which in hexadecimal form is 0x4ef7.

Figure Hexadecimal representation of the file. The highlighted bytes lie exactly at the start of the offset bytes from the beginning of the file. The preceding 0x0a bytes is the new line and the current 0x31 bytes represents the number 1, which is exactly the start of the xref table. This is why the xref table is represented with an indirect object with an ID 16 and generation number 0. This should be the case for all objects, since we just created the PDF document and none of the objects have been changed yet.

If we look at the whole PDF document we can see that this is clearly true; all objects have a generation number zero. The first integer specifies the first object number in the subsection and the second integer specifies the number of entries in the subsection. In our example, the object number is zero and there are 17 entries in this subsection. Note that this number is one larger than the largest number of any object number in the subsection.

Those two strings are used as input to the encryption algorithm. In our case, the length of the encryption key is 60 bits. Why would we write a program for that if a tool already exists? After that, the out. Figure xref and trailer. We can see that there are 14 objects in the xref table. We could go on and try to decode other sections as well, but this is out of the scope of this article. We must know by now that all PDF documents should be read from the end to the start.

The trailer is represented in the picture below:. Figure Object We can see that the object is indeed the Document Catalog. The Page Tree object with an ID is represented in the picture below:.

Figure Page Tree object. So the object contains the actual pages of the PDF document. It contains 10 pages, which is exactly right we can check this out if we open the PDF file with any PDF reader and check the number of pages.

We know that the Kids attribute specifies all the child elements directly accessible from the current node. In our case, there are two direct child nodes with object IDs 66 and Object 66 is presented below:.

Any way of doing that? Looking at the raw code of PDFs will not serve you much unless you also have an idea about its internal structure. You should get yourself a copy of the official PDF reference download PDF , and you should have read some introductionary article such as this [gone] or this to begin with.

Even after such a preparation, you'll not discover much useful when staring at the raw code. Because PDFs usually will contain parts which are "filtered" that means: compressed.

Jay Birkenbilt's qpdf is a very useful commandline tool available for Linux, Mac OSX and as source code, under the open source Artistic License , which can unpack most filtered content and re-organize the internal structure in a way that gives you much more insight into it all objects are numerically ordered, etc.

The commandline to achieve this is:. This one even comes with a GUI if you prefer that , while still allowing you access to the internal structure and "raw" PDF code.

Use a Hex editor. If the purpose is just to look into the file, then any simple text editor will do, ex, Notepad. PDF is just a text based format, including embedded content byte streams. Raw PDF looks like this:. What you see are basic COS objects like name, dictionary, stream and so on. All objects are described in PDF standard, see section 7. In addition to the qpdf tool conversion into postscript might be helpful.

PDF is a subset of PS. Usually its quite easy to figure out, e. You can either use pdf2ps or invoke ghostscript. When you generate your PDFs using pdflatex you can disable compression with an option. This makes the PDF more readable. Create a free Team What is Teams? Collectives on Stack Overflow.