Low Quality when PDF export

[itay316457824f3x]

Hi,

I am designing a poster for a magazine and when I am exporting to PDF only the text look in high resolution, all the image gets really blurry but in Photoshop file they are in very high-quality (look image)
My document size is 28x22 centimeters with resolution of 400
I have tried to change the settings of the PDF export with no luck
What else can I do?
Thank you in advance

[itay316457824f3x]

Anyone?