When i make the pdf i see in Illustrator that the fontsize is changed.
If i for example set the fontsite to 7 in the pdf de fontsize is 6.75 and when i set the fontsize to 14 the size in the pdf is 14.25. This results in not so clean looking texts in the definitive document. Any solution for this?
The font size is in "points", where 1 point is equal to 1/72 inches. So a font size of 7 point will be 7/72 inches.
In a computer screen, the display is in pixels. In most GUI, it is customary to assume 96 pixels per inch. So 7/72 inches is 7/72 x 96 = 9.333 pixels in size.
But rendering fractional pixels would become very ugly on a computer screen. As ChartDirector is optimize to display on screen, it will round the size to 9 pixels instead. When converted back to font unit, it is 9 x 96/72 = 6.75 points.
In other words, 6.75 points is used because it creates the best looking text on a computer screen.
Are you viewing the PDF on Windows at a zoom level of 100%? If this is the case, the 6.75 points should become 9 pixels, and the display should be optimal. However, if the zoom level is not 100%, it may result in fractional pixels and the PDF viewer may not be able to render the text as clear.
Also, to ensure clean looking text at small font size, please use high quality fully hinted fonts suitable for screen display. Most fonts that come with Windows or macOS are high quality fully hinted fonts suitable for screen display. However, if you download a "free font" from the Internet, it is very likely it is not properly hinted. In this case, the font may look good at a large font size or when printed on paper, but not too good at small font size when displayed on a computer screen. That's why in many free font downloading sites, they only show the fonts in large size.
For testing, you may try to create a chart using some known good fonts such as Arial, and view the PDF at 100% zoom level. If you still think it is too blurred, would you mind to email the PDF to me for testing? By email is email@example.com