Learn the Ins and Outs of PDFs

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Tech corner

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 ...

Tech corner

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?

Tech corner

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 ...

Tech corner

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?

Tech corner

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 ...

Tech corner

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 ...

Tech corner

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 ...

Tech corner

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 ...

Tech corner

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". ...

Tech corner

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 ...

Tech corner

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 ...

Tech corner

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 ...


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