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Finding Resolution of PDF

dnalyn
Registered: Apr 9 2007
Posts: 2

I'm a graphic designer and we often receive pdfs that someone will want us to edit. The problem is that these often have to be printed. Are there any features within Acrobat Professional where you can determine what resolution a particular document was saved as?

My Product Information:
Acrobat Pro 8, Windows
thomp
Expert
Registered: Feb 15 2006
Posts: 4411
The drawn page content on a PDF is by nature vector graphic based. It has no resolution. The print resolution is determined by the RIP. That said, images used in the PDF do have a resolution, and color space. You can get an analysis of images and convert resolutions and color spaces with the PreFlight and PDF Optimizer tools on the Advanced menu.

Thom Parker
The source for PDF Scripting Info
www.pdfscripting.com
Very Important - How to Debug Your Script

debbiek
Registered: May 9 2009
Posts: 3
I'm a long-time print designer and am now getting pdf files from people with photos, ads, etc. to be imported (placed) into InDesign CS4. I don't want to learn all about pdf files, however I guess I need to. My questions are all in relation to resolution and PDF files. Thomp mentions above the "drawn page" content on a pdf is vector based. What does "drawn page" mean? Does this mean the text in a pdf image is always automatically vector based and will print out at whatever res. the InDesign document is being printed? If that's true, the images in a pdf doc are the only concern in relation to dpi, right? The same response says that images used in the pdf do have a resolution, so then I went into Preflight as suggested, and I don't see a place where it gives the resolutions (in dpi), of the images in the .pdf file I've been sent. I need to know how to find out what dpi images (and text) were saved in and then inserted in the pdf so I know if they are high enough quality to use.
-What directions do I give people to make sure they are giving me pdf files with 300 dpi minimum pdf images/files?
Thank you very much!
UVSAR
Expert
Registered: Oct 29 2008
Posts: 1357
debbiek - yes, you're right. In a PDF the elements which can be drawn on the fly are always vector-based:


- text
- smooth gradients and fills
- lines and curves
- images embedded as EPS data

Bitmap (raster) images are of course stored in pixels, but unlike in creation packages such as InDesign, when Acrobat has to flatten a vector (say a drop shadow) it does it dynamically, so the pixel res is chosen by whatever your printer settings require it to be. There's no concept of "document raster settings" in a PDF file.

In Preflight there are a few "check only" profiles you can run to find images under a certain resolution - plus whenever you run a preflight check the report on the screen (the tree of info) always ends with the summary of document contents. You can drill down into that summary and see the info about any element (image, etc.) including pixel res, color space, transparency, etc.

If people are sending you PDFs then the pixel res of their images (and the compression level) is set by whatever they made it in. Using Adobe products, it's the Distiller preset which matters. Choosing "Press" or "PDF/X-1a" will keep them low-compression and high-res, typically 300dpi (or whatever the image was if it's not that good to start with). As you may not know what software they're using, it's normal to just specify a PDF version, resolution and color space and let them work out how to achieve it. If you ask for /X-1a then you know all the files will be CMYK 4-plate with embedded fonts, but they can still have a 72dpi photo on page 3 if that's what the person started with! /X-1a flattens out layers and makes everything process, which is good for "dumb" print but as you're imposing in IDCS4 you can read layers and spot, and may need them still intact, so the other presets like /X-3 or "Press Quality" might be better suited to your workflow. The problem of course is if you're getting layered files, the client may not have understood overprinting and will grumble the result doesn't look like it did on their monitor!

April's Topic Of The Month was all about printing and pre-press, and has a lot of tutorials on using Preflight - check the Learning Center at the top of this page.