I'm using /usr/bin/pdftk filename.pdf dump_data_fields output - flatten to get the FDF fields in a PDF but it seems to be including invisible FDF fields as well.
https://docdro.id/nriB59b is a one-page PDF without any txt but with a number of these invisible FDF fields. pdftk's output can be seen at https://pastebin.com/ag6vweNP.
How can I exclude invisible FDF fields?
I'm currently using pdftk but I'm open to using other tools as well.
Thanks!
My guess is you have to inspect the PDF yourself to detect if or not a field is invisible. In another side, it may become very tricky to tell if a field is invisible or not, except if a flag sets this.
For example, although I don't know if it's possible, but let say a field is outside the page or covered by another content... Is it visible or not?
By the way, you can use qpdf to inspect the content of a PDF file. The following command will decompress your pdf to get it human readable.
qpdf --qdf --object-streams=disable orig.pdf uncompressed-qpdf.pdf
If you prefer a JSON representation:
qpdf --json your_pdf.pdf > your_pdf.json
If you go for the later one, you can parse the json output with jq.
Then, use the PDF speficication you want to apply. I suggest also these steps:
you produce a pdf with a given field visible
another copy of this pdf but with the field hidden
uncompress both of them and then compare them with diff.
Related
I want text with exact format and layout from pdf.
If pdf to text is not the direct choice, is it possible to do pdf -> xml -> text?
I have already tried PyPDF2, pdfminer and pdftotxt. Even I've tried using AWS textract and got incorrect layout.
Basically if I can construct sentence from the text extracted from pdf, that's enough.
I used Zamzar API which gives exact output but they're quiet expensive.
Any possible solution?
If you are looking to keep the structure of the PDF but not the font, colour, size etc., then try the pdftables_api library. This should hold the layout of your PDF. Convert PDF to CSV as a CSV file is just a comma seperated text file.
If you are looking to keep font, colour etc., Zamzar API is probably your best option.
I'm using pdftotext to extract info from a pdf. Currently using the -raw option. I do have a few problems with the PDFs I'm working with. If I select the text from top to bottom it selects in the following fashion.
PDF content:
A
B
C
It selects A then C and then B. So when I extract the text it is presented in the same way. Is there a way to reformat the PDF so I can select the content from top to bottom?
NOTE: I'm aware that if I omit the "raw" option the layout will be preserved, but it seems to be buggy when the document includes tables so raw works better for me.
Yes, you can reformat the PDF so that the content is returned from top to bottom. This is not something that can be easily done using Adobe Acrobat or any other viewer that I am aware of and here is why.
From the documentation of pdftotext, the -raw option is defined as
Keep the text in content stream order. This is a hack which often "undoes" column formatting, etc. Use of raw mode is no longer recommended.
"content stream order" is the important piece in the description.
In PDFs, the content on the page does not have to be written in the content stream (the instructions that are interpreted to display the page) in the order that a human would read the content when the page is rendered. The internals of PDFs do not care about the ordering, they were designed to reproduce the same visualization of a document on a variety of platforms. Since all that matters to PDF is the visualization, applications or libraries that write PDF tend to not order the content stream in any meaningful way.
So you can reorder the instructions in a content stream so that they are in the order a human would read them, it is not an easy task to do by hand and using a library that understands PDF to manipulate the content stream would be one way of doing this. Another way is to look for a more advanced tool to use to extract text from the PDF (there are a number of tools that will look at the placement of the content on a page rather than just where it appears in the content stream).
I am not aware of anything that will reorder the content stream in the PDF based on where the content appears on the page automatically though.
I'm trying to hide a file in a PDF file code. I've already search some information to help me. I've tried to uncompress the pdf using pdftk ( pdftk pdf.pdf output uncompress.pdf uncompress ). Then I tried different things such as :
Insert commentary : I put " %TEXT_TO_HIDE " in the uncompress pdf file code.
add new object : I put " 0 0 obj << TEXT_TO_HIDE << endobj " in the uncompress pdf file code.
modify an existing object
then i compress it using pdftk again
In each case, I obtain a new pdf, which is looking different from the original. It's not corrupted but images have different colors, and some original text are missing.
So, do you know some rules to change a pdf code without anyone notice ?
(PS : Sorry if my english is bad ^^ )
You cannot modify a PDF file in a text editor and expect the file to be still compliant in general. PDF is a binary format and you need to read the PDF specification to figure out how to modify it.
That said, there are heaps of places where you can "hide" information in a PDF document, the real question is how much data you want to hide, and to what purpose. The purpose typically links to how secure exactly this needs to be.
As some examples:
1) PDF allows embedding complete files in the actual PDF file. This is not really secure as anyone with decent software can extract these files (but the file itself could still be secured of course).
2) PDF allows adding arbitrary objects anywhere (or almost anywhere) in the file. This is a great way to hide information, but someone with the right tools can browse the object tree (even if the file is compressed) and see what you did.
3) PDF allows adding for example white text on a white background or text behind other objects. Again, there are ways around this for people with the right software.
4) Adobe's PDF spec allows at least 1K of fluff after the %%EOF marker (although ISO 32000 does not). Keep in mind that this is visible to anyone opening the file with a decent text or binary editor. (Thanks Jongware).
In short, you need to define much better what exactly you want to accomplish and how "secure" secure is in your use case.
You should also consider how "robust" the method must be. Should someone be able to save your PDF file with Acrobat for example with the hidden code intact? Some of the above methods may not be robust enough to ensure that with absolute certainty.
I have to make several certificates with the same design but different names. So I've tried to make an uncompressed pdf file with a place holder text and tried to change it with a text editor. For some reason it didn't work. I could only see a single letter of the replaced text.
When I try the same thing with an eps file, it works but since eps doesn't keep (AFAIK) page orientation, there is a chance that it something will be different with different names.
Does anyone know why this didn't work or how to change a text box in a pdf file (with sed)?
(I created the master pdf with Illustrator CS4)
Thank you
In general, editing PDFs in a text editor is a Bad Idea. PDFs depend on the byte offsets of various objects to not move.
If you KNOW your editor won't change the EOL bytes (or what it thinks are eol bytes), and you DO NOT change the length of the text entry's object as a whole, you're okay.
For example:
1 0 obj
<</Type/Annotation/Subtype/Widget/V(PlaceHolder Value)/T(Field Title)...>>
endobj
If your new value is longer than "placeholder value", you're screwed.
Most PDFs contain quite a bit of compressed binary data. Some of that data WILL be misinterpreted as EOL characters. Changing them will:
a: break your compressed stream
b: possibly change the byte offsets of the rest of the PDF.
When I hack on PDF files, I always use a hex editor.
Bottom Line: Don't mess with PDFs as a text stream. Mess with them as PDF files, using a PDF library. There's sure to be one capable of altering form field values in your language of choice.
You can also look into FDF and XFDF to see if they'll suit you better. Both file formats store field/value pairs and a reference to the form to use with those pairs. FDF uses PDF's syntax, while XFDF is an XML grammar. You can serve the [X]FDF to your end user and they will see the filled-in form.
WARNING: Unless the form is Reader Enabled (requires Acrobat (pro?)), they won't be able to save the version of the form they get after opening the [X]FDF, only view/print it. Of course they can save the [X]FDF, but many users might balk at this Strange New Format.
This question already has answers here:
Merge / convert multiple PDF files into one PDF [closed]
(23 answers)
Closed 6 years ago.
I have 16 pdfs that I want to convert into a single one... I am on Ubuntu 10.10, how can I do it?
First, get Pdftk:
sudo apt-get install pdftk
Now, as shown on example page, use
pdftk 1.pdf 2.pdf 3.pdf cat output 123.pdf
for merging pdf files into one.
You can also use Ghostscript to merge different PDFs. You can even use it to merge a mix of PDFs, PostScript (PS) and EPS into one single output PDF file:
gs \
-o merged.pdf \
-sDEVICE=pdfwrite \
-dPDFSETTINGS=/prepress \
input_1.pdf \
input_2.pdf \
input_3.eps \
input_4.ps \
input_5.pdf
However, I agree with other answers: for your use case of merging PDF file types only, pdftk may be the best (and certainly fastest) option.
Update:
If processing time is not the main concern, but if the main concern is file size (or a fine-grained control over certain features of the output file), then the Ghostscript way certainly offers more power to you. To highlight a few of the differences:
Ghostscript can 'consolidate' the fonts of the input files which leads to a smaller file size of the output. It also can re-sample images, or scale all pages to a different size, or achieve a controlled color conversion from RGB to CMYK (or vice versa) should you need this (but that will require more CLI options than outlined in above command).
pdftk will just concatenate each file, and will not convert any colors. If each of your 16 input PDFs contains 5 subsetted fonts, the resulting output will contain 80 subsetted fonts. The resulting PDF's size is (nearly exactly) the sum of the input file bytes.
You can use http://www.mergepdf.net/ for example
Or:
PDFTK http://www.pdflabs.com/tools/pdftk-the-pdf-toolkit/
If you are NOT on Ubuntu and you have the same problem (and you wanted to start a new topic on SO and SO suggested to have a look at this question) you can also do it like this:
Things You'll Need:
* Full Version of Adobe Acrobat
Open all the .pdf files you wish to merge. These can be minimized on your desktop as individual tabs.
Pull up what you wish to be the first page of your merged document.
Click the 'Combine Files' icon on the top left portion of the screen.
The 'Combine Files' window that pops up is divided into three sections. The first section is titled, 'Choose the files you wish to combine'. Select the 'Add Open Files' option.
Select the other open .pdf documents on your desktop when prompted.
Rearrange the documents as you wish in the second window, titled, 'Arrange the files in the order you want them to appear in the new PDF'
The final window, titled, 'Choose a file size and conversion setting' allows you to control the size of your merged PDF document. Consider the purpose of your new document. If its to be sent as an e-mail attachment, use a low size setting. If the PDF contains images or is to be used for presentation, choose a high setting. When finished, select 'Next'.
A final choice: choose between either a single PDF document, or a PDF package, which comes with the option of creating a specialized cover sheet. When finished, hit 'Create', and save to your preferred location.
Tips & Warnings
Double check the PDF documents prior to merging to make sure all pertinent information is included. Its much easier to re-create a single PDF page than a multi-page document.
There are lots of free tools that can do this.
I use PDFTK (a open source cross-platform command-line tool) for things like that.
Also seem pdfjam: http://www2.warwick.ac.uk/fac/sci/statistics/staff/academic/firth/software/pdfjam/