Editing PDF files can cause problems

The problem with editing PDF files

by Dean Cook, June 10, 2016
Category: Blog,   Tags: applying changes to PDF files, edit, edit a PDF, editing PDF, making a quick change in a PDF, PDF problems,

Ah, so you have a PDF file on screen and you would like to make changes. Easy, yes? Well, not really. Dean Cook offers why applying changes within a PDF file isn’t such a great idea.

We’ve all been there; you have a PDF file of an advert on your computer screen but you need to make changes. So, what do you do? Should you attempt to make changes within the PDF file as it appears to be the quickest option, or do you contact the originator to make them for you which could take a while before you see another PDF?


The PDF (Portable Document Format): a very different file format

The PDF file is very much a different kind of format compared to the ones that construct documents, images and illustrations. There are no programs that use PDF to build documents from the ground up. Instead, users utilise pro-tools such as InDesign, Illustrator and Photoshop – as well as Word, Excel and PowerPoint etc. – then, after the work is approved, a PDF is exported/generated  for its intended output.

While the original program’s raw file format shows you what you can see on screen, it also holds all the necessary background data too (text, fonts, formatting, images, vector elements, styles, objects, filters, master elements, tagged information, external links, profiles, etc…).

The PDF file, on the other hand, only holds the essential visual content at the specified resolution for its intended output purpose. All images are cropped, resampled and embedded; and all of the non-essential background, editable features and structured information are removed. This optimises the data and encapsulates a file format purely for viewing and output. It also reduces the risks of inherent problems occurring in later processes.

It is possible to make limited alterations (also known as ‘patching’) to PDF files but it should only be pursued if the original artwork file ‘doesn’t exist’. Changes should ideally be applied by a competent designer, having access to Acrobat Professional, to ensure alterations still meet the required technical standards. They need to work around the fact that although you can see text, the structure of that text does not exist. Many features, which you would generally take for granted, are not available. As a typical example, paragraph copy will not reflow if you need to add/remove a word or two. And as for applying tracking/kerning so the change doesn’t look so obvious, well that’s another story.

Other issues are mainly font-related. Although the font information is more than likely to have been embedded into the file, you need the actual font available on your system to apply those changes. If the font isn’t available then any changes may substitute for a font style which may look very much different in appearance.


Making changes to Photoshop- / Illustrator-saved PDF files

On many occasions, we may receive flattened Photoshop- or Illustrator-saved PDF files in which case editing copy is only made more difficult. The text that was originally applied in the Photoshop file has now been converted to pixels; the text in Illustrator has been outlined as graphical shapes/objects (vector) therefore rendering themselves uneditable.

• There is an exception with Illustrator saved PDF format where editable features are still enabled but do lend to colossal PDF file sizes making them less efficient to send to recipients. Users are able to optimise and reduce Illustrator PDF files, and we can show you here how to do it: click this link.


The correct way is the only way

Any professional designer would advise against editing PDF files because of the issues explained above but also those changes wouldn’t be applied to the original artwork either; therefore, original errors will reappear the very moment another PDF is exported from the raw files.

No matter how minor the change, while possibly a tad time-consuming, it is imperative that the original artwork is kept up to date. This makes for easy dispatch of PDF files for the variety of output options. This way not only will the artwork always be correct but it’s also going to be visually and technically free from errors and optimised for output too.



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