The problem is that there is binary information you're ignoring -- some of that information may no longer be valid after modifying only the human-readable portions. For example, some of that binary information could be a "directory" or "table of contents" -- containing information about segments of data contained within the file (e.g. relative position within file, length of segment of data, and possibly some form of data integrity check information such as a checksum or CRC value). In short, only altering the human-readable portions of the file may not be sufficient.

>I have already succeeded in what I want; but that was Manual exercise, by Editing in a Notepad. So not possible to do it for thousands of files and thousand of times So now trying to do it through a code.
>
>I don't think its always necessary to understand the entire language / format first to achieve some task. If it would have been so, it will take a month to first understand the format and do further task on it.
>
>Thanks Anyway.
>Regards
>Harsh
>
>
>
>
>>You forgot to first step - study PDF format.
>>
>>MartinaJ
>>
>>>Yes But I am giving a Hard Try to Make it Readable. By comparing it other readable such types of PDF.
>>>Thanks
>>>
>>>Yes, it's PDF, but this ways is very bad way how to change content of PDF. Changed file will be unreadable.
>>>
>>>
>>>>
>>>>MartinaJ
>>>>
>>>>>The complete sample PDF Files are attached herewith. I am trying to repair or you can say edit these Files by going inside the files.
>>>>>
>>>>>https://www.dropbox.com/s/ortwm9qyyx7i542/Sample.7z?dl=0
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>>I give up! You keep on repeating yourself instead of answering my simple question. What's so difficult with providing some sample, a la this:
>>>>>>
>>>>>>1. Data: 'fsdjfsdsdlfds' I want 'dsd'
>>>>>>2. Data: 'dfgdføfdfgdf' I want 'fdf'
>>>>>>
>>>>>>Please read the question we ask!!!!! We don't know what you know, so you must tell us what we ask for!
>>>>>>
>>>>>>>Sir Here is the link with Real Data. in Text File
>>>>>>>
>>>>>>>https://www.dropbox.com/s/p2ud6aknblqwxw3/123Data.txt?dl=0
>>>>>>>
>>>>>>>I need to do what STREXTRACT() do it for records.
>>>>>>>
>>>>>>>i.e want to extract string between _123456789 and /Mediabox in all the cases and replace that extracted Text with my own Specific string.
>>>>>>>
>>>>>>>Each of the above extracted String so extracted will be replaced by each Unique string.
>>>>>>>
>>>>>>>Thanks
>>>>>>>
>>>>>>>
>>>>>>>>I am no mind reader, soI try a third (and last) time: Please show some realistic data, and what you want as a result. The more samples the better.