Creating SAME SIZED pdf from two pdf's

Question

i am probably not following instructions very well and i am not finding an explanation in the documentation so i am hoping someone can help me out here.
i have two pdf's. one is a cover page of a magazine and the other is a page inside the magazine where my work is mentioned. i wish to combine these two pdfs into a SINGLE pdf but in a way that both the pdf's are the same size. i feel like i am missing a settings somewhere for this as each time i do this the inside page is printed into the pdf document at half the size of the cover page.
i have tried saving out as png and making sure they are the same size and resolution but this prints (out of Preview) with white borders all around.
i have tried saving out as Optimized pdf and setting the sizes to 8 x 11 and 72 dpi but this then prints out of Acrobat as a highly rasterized document that is unreadable.
can anyone help me with a step by step on how this can be done? it seems like i should just be able to open two random pdf's in the CREATE pulldown and then tell Acrobat to print them at some specified size (this would be very easy!) but i must be missing something.
TIA

Answer 1

Hotwheels 222,
It might help to think of PDF as a container that can have many things such as text, photos, graphics, vector elements,etc all wrapped up inside it.
Normally the content is created in another application such as InDesign, Illustrator, MS Word, or many other appliations. In the application you create a blank document and add or place images, type text in any font you desire, place or create some vector elements (if the application actually have any vector tools), and even other multimedia like audio/video as long as the application supports them,
The photos can all have a different resolution, the vector elements have no resolution (I'll explain), the text may be in many different fonts and they all retain their separate characteristics inside the PDF.
A PDF created from an application like Photoshop will just have one resolution because PS is a pixel based image editor and a PS document can only have a single resolution.
. . .the idea that two adobe products cannot communicate from acrobat to photoshop in terms of a pdf resolution in photoshop seems very inconvenient. . . Again, since a PDF may have many photos with different resolutions, even if PS could get this info (which it can't) what resolution should PS decide to use? PS leaves this up to the user to decide based on what they want their final output may be.
You mention a document you have that "appears to be no images inserted" and "it appears as if it is one image"?
Are you referring to the Cover pdf?  The PDF producer is "Adobe Acrobat 10.0 Image Conversion Plug-In" is a tip off to "Test Screen Name" and myself that it came from Photoshop. 
While its possible this document was completly created in Photoshop, it is also likely that it was created in another application like InDesign, etc. exported from there as a PDF and then the PDF was opened in Photoshop which rasterized the content and flattened it into a image file with the resolution that you chose when opening in PS and then saved again as just an image in the PDF format. The graphic artist that created this probably did this because they didn't want to give you a print quality PDF that you might try to extract elements from.
You mentioned you thought the doc was from Adobe Illustrator (AI)  AI is primarily a vector creation tool which also allow for the inclusion pixel based raster images (with a specific pixel resolution) to be placed in an AI document if wanted.  Strictly speaking, vector objects don't have a resolution. They are based on math,
It basically says, place a point at such & such X, Y coordinates, now place another poing at some other X,Y coordinates, it takes into account the arc or angle between the two points and says draw a straight line, or draw a curved line ,etc. Since these are only mathematical instructions. this can be enlarged as big as you want and the relationship between the 2 points and the arc of the curve or line will dictate how the enlarged line or curve will be redrawn. 
Vectors are "resolution independent" you can draw a vector logo at 1 x1 inch, and enlarge it to 50 x 50 inches or even as large as a house and it will still print crisp and clean. Note, this only applies to the vector content in your document; any pixel content is stuck at the resolution it was created at.
To inspect elements in a PDF use the Object Inspector in Acrobat Pro. Since a PDF may contain many differing objects you need to click exactly on each object to get any info about the selected object. So if you had 10 photos in your PDF you would need to select each in turn and it would give you the pixel dimension, resolution, color space and profile, etc. if you clicked on text it will identify the font. It is well named, an Object Inspector rather than a Document inspector. Try it yourself with different PDFs you may encounter. If for example, it gives you the exact same info (resolution, pixel dimensions. etc) no matter when you click, then you are likely dealing with a whole single image. If you get different pixel dimension, resolutions when you click in various different areas you are dealing with a PDF that had separate distinct elements.
. . . i can't see why i shouldn't be able to get a document that is 17.7 x 22.9 at 72 ppi down to one that is 8 x 11 at 300 ppi.
In Photoshop, go to the Image menu, Image Size. This will show the pixel dimensions (width & height) at the top. If you don't interpolate (Resample) Photoshop can only put the same number of pixels into different size documents. When you squeeze the same # of pixels into a smaller doc the resolution goes up. When you place the same # of pixels in a larger doc the resolution goes down.
Remember, that resolution is PPI (Pixels Per Inch)! If you do the math this will start to make sense.
Below note that each dialog box has the EXACT same pixel dimensions.
In the first box it shows the 1275 x 1650 pixels in a document of  17.708 x 22.917 inches. This yields a resolution of 72 PPI.
In the second box I changed the document size to 8.5 x 11 inches and the same 1275 x 1650 pixels now increase the resolution to 150 PPI.
In the third box I changed the resolution to 300 PPI and the same 1275 x 1650 pixels now decrease the document size to 4.25 x 5.5 inches.
If you click the Resample Image box, Photoshop will interpolate (resample) the image by throwing away pixels or by adding pixels, but there is no magic involved, and the results are never as good as one might hope for.
Like Goldilocks and the 3 Bears, some things are best when they are "just right"