There is no Pentax A 25-135mm f/4, but there is a Pentax A 28-135mm f/4.
Pentax lenses will not mount directly onto a Canon EOS body (like your DSLR). You can get cheap adapters from e-Bay. but I do not recommend this.
That lens is all manual and even if it was not, when used on a Canon via an adapter it would only work manually (that's manual focus, manual aperture).
What you need is lenses that are compatible with the Canon EF and EF-S mounts, which, for your purposes, will allow all automated functions the lenses support. Sigma and Tamron also make lenses which are compatible with Canon EF/EF-S but be careful because they also make the same lenses for Nikon and other DSLRs, which will not be compatible with your Canon.
The world of lens-body adapters is full of pitfalls and devil-in-the-detail issues for the unwary, so I really do not recommend it until you have a lot more knowledge under your belt.
However, if you particularly want to pursue this the kind of adapter you would need is something like this.
Please note that this is not a product recommendation, but to show you the kind of think you need. Not all adapters will, for example, allow focus confirmation to work, while this type claims to.
I am assuming you have a kit lens (an 18-55) for your Canon. Those are actually pretty good lenses and if you want to invest in a lens as a "next step" I'd suggest a used Canon 50mm f1.8 would be the best choice. That will get you into wide aperture shooting and fixed focal length primes. They're typically used for e.g. head-and-shoulder portraits with strong background blurring (but this isn't their only purpose).
There's a similar budget option called the Yongnuo YN 50mm f1.8 for about the $50. There's an informal review of it here for those who are interested. They certainly are not a well known name in lenses (they're well known for cheap flashes, however).
Again I cannot (site rules) recommend any specific product, but this is the kind of thing to consider.