Learn the Ins and Outs of PDFs
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Converting invoice documents to the ZUGFeRD data format
XML or PDF? That's one of the most heard questions when it comes to invoice document formats. XML is the preferred format for machines whereas PDF is the format for humans. But why not have the cake and eat it? With ZUGF ...
Is the PDF version information a neglectable detail?
Each PDF file starts with a header comment that carries version numbers. What do they mean? Can a reader ignore these numbers or what is it to do? Is there any other version information that a reader should take care of?
How to avoid implementation dependent appearances of annotations and interactive form fields
Annotations such as notes and links belong to the most appreciated PDF features. Although they are easy to use from a user's perspective this is certainly not true from a developers perspective since it is often not clea ...
The PDF Forms Babylon - AcroForms and XFA
PDF forms are very popular among users. A tools programmer can, however, choose between two different forms systems: AcroForm and XFA. When to choose which and why?
Font conversion - what's this good for?
The native font format of Microsoft Windows is TrueType. The PostScript fonts are not very well supported on Windows and the Type 1 format has even been discontinued. On the other side some embedded computers of printing ...
Vertical writing - Not just a matter of fonts
In some writing systems you can place the characters vertically from the top to the bottom to form you sentences. Most users know this from Chinese, Japanese and Korean texts. What does it take to use the vertical writin ...
How to preview overprinting
Some printing machines can print colors on top of others and some cannot. Some PDF viewers offer an optional preview function that simulates the effect of overprinting on a display screen. Since this function is not spec ...
How to transform spot colors without ambiguities
On an RGB screen or a CMYK laser printer spot colors cannot be displayed directly and must be emulated by converting them into their process color equivalent. The Separation and DeviceN color spaces provide tint transfor ...
Clear up some myths about PDF printer drivers
I'm sure you've heard sometimes phrases like "a printer driver which is based Windows GDI can only reproduce RGB colors" or "if a printer driver isn't built on top of the PostScript driver one cannot print EPS graphics". ...
The art of repairing damaged PDF files
I sometimes got a little shock when I wanted to open a PDF file and the viewer only showed an error message. In some cases, however, the viewer can save the file and repair it, but often not. This experience made me thin ...
What can I do about sliced images?
If I try to extract images from a PDF file it sometimes happens that I get a bunch of slices of the original image, mostly consisting of a few image rows per slice or, in extreme cases, just one row. Why is that and how ...
PDF validation with customer specific extensions
While talking about PDF validation workflows I often come across questions like "Can I let the validation fail if the paper format does not match our corporate rules?". This and other customer specific requirements are i ...