In the print dialogue window, make sure the paper is set correctly (e.g. to A4 and not Letter) and that the print size is set to 100% (i.e. 'page scaling' is 'none' / 'reduce to fit' is not checked).
Also, make sure the paper is snugly nestled in the paper tray. Sometimes if it sits too loose it can shove around a couple of mms while being picked up for printing.
When a printing company talks about 'resolution' requirements for images, they almost always specify 300dpi (dots per inch).
In digital images, 'dots' are equivalent to pixels.
So, as an example, in a design where the image is to be printed at a size of 5 inches by 4 inches, the digital source image should be 1500x1200 pixels or more.
In practice, the resolution can be somewhat lower, say 240dpi, without noticeable loss of quality.
For comparison, a web image is always 72dpi – much lower! This is why images taken from the web are often unusable for print.
The key factor is always pixel size rather than the resolution the image is according to the computer software.
When supplying images, whether for print or for web, it's best to provide the original image.
The default choice is PDF: this is a universal format that can be read by every computer.
If you want to make it accessible to other devices, such as tablets, it should be offered in the EPUB format. To be read on Amazon's Kindle device, it needs to be in the MOBI format.
What is the production process?
Your original source file will typically be in Word (DOC) format. From this, IDstream will create the fully-designed file (using Adobe InDesign). The file can then be exported to whichever format(s) required.