TIFF is a raster image. It has a DPI property to tell how long in inch the width or height of the image is.

When converting tiff to pdf, the default pdf DPI is 72, which means 72 pixels per inch.

So if you want to keep the pdf page size as large as the orignal TIFF image in inch, you can do it with the new method of the tiff to pdf component.

SetImageScaleRatio(LONG xScalePercent, LONG yScalePercent)
xScalePercent: the percent of PDF DPI ration (72) against the orignal image x DPI
yScalePercent: the percent of PDF DPI ration (72) against the orignal image y DPI 

For example, if you TIFF has DPI 200, the scale ration is 100*72/200. What you need to do is to call this method before converting.

After doing this, the pdf page can be in same inch to the tiff image. And the image quality doesn’t degrade as well.