I have 2 logos saved in a PDF file. I sent them to my printer to have a banner printed using those logos. THe printer is saying they are not high enough resolution. How can I reformat them so they are usable for my banner? Thanks in advance.
You cannot "reformat" the PDF in a way that will make it appropriate.
You can do things to extract the image, and you can fuss with the numbers (pixel dimensions, dpi) so that the resulting file will conform to their specification. However, this will only play with the numbers and the quality will be the same as if they just used the PDF you submitted, since you will be doing exactly what they would need to do to get it to print at the size you requested.
What you need to do is go back to the the assets used to create the original item and then recreate the item, targeting the correct pixel dimensions and print size. If it is full color, not primarily line art, you would be going for 300dpi, so you need 300 pixels per inch per dimension. for 10x10 inches, this would be a 3000x3000 pixel image. You will probably want to avoid saving it as a jpg, since this will degrade quality a little.
If it is a logo or primarily line art and large areas of solid color, you probably want vector art (illustrator, eps), which is device independent and not measured in pixels, generally.
If you can't get a better quality image or don't have access to the original assets, you may need to recreate it. Otherwise, you will need to make a judgement call: decide if the low quality as submitted is going to be good enough.
It will depend on how the image are stored in your own PDF file: as you can see in this Wikipedia article about the PDF imaging model, the image could be either vector graphics or raster graphics.
You should be able to extract images from your PDF using tools such as Some PDF Images Extract.
In the case of vector graphics, you would be able to upscale them easily. If they are raster graphics, you can use your favorite image editor but be careful about which upscaling algorithm is used!